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In Excel 2007, how do I add a description and parameter hints to a user-defined function? When I start typing a function invocation for a built-in function, Excel shows a description and parameter list--a tooltip. I'd like to do the same for the functions I define.
Not just for the formula insert wizard, but in the formula box, so if I key "=myFun(", at the "(" the tooltip pops up just like it does for "=average("
There's no help in VBA Help, none on MSDN and none on any of the Excel and VBA dedicated forums I can find, so this is clearly a long shot.
Not a tooltip solution but an adequate workaround:
Start typing the UDF =MyUDF( then press CTRL + Shift + A and your function parameters will be displayed. So long as those parameters have meaningful names you at-least have a viable prompt
For example, this:
=MyUDF( + CTRL + Shift + A
Turns into this:
=MyUDF(sPath, sFileName)
Professional Excel Development by
Stephen Bullen describes how to
register UDFs, which allows a
description to appear in the Function
Arguments dialog:
Function IFERROR(ByRef ToEvaluate As Variant, ByRef Default As Variant) As Variant
If IsError(ToEvaluate) Then
IFERROR = Default
Else
IFERROR = ToEvaluate
End If
End Function
Sub RegisterUDF()
Dim s As String
s = "Provides a shortcut replacement for the common worksheet construct" & vbLf _
& "IF(ISERROR(<expression>), <default>, <expression>)"
Application.MacroOptions macro:="IFERROR", Description:=s, Category:=9
End Sub
Sub UnregisterUDF()
Application.MacroOptions Macro:="IFERROR", Description:=Empty, Category:=Empty
End Sub
From: http://www.ozgrid.com/forum/showthread.php?t=78123&page=1
To show the Function Arguments dialog, type the function name and press CtrlA. Alternatively, click the "fx" symbol in the formula bar:
I know you've accepted an answer for this, but there's now a solution that lets you get an intellisense style completion box pop up like for the other excel functions, via an Excel-DNA add in, or by registering an intellisense server inside your own add in. See here.
Now, i prefer the C# way of doing it - it's much simpler, as inside Excel-DNA, any class that implements IExcelAddin is picked up by the addin framework and has AutoOpen() and AutoClose() run when you open/close the add in. So you just need this:
namespace MyNameSpace {
public class Intellisense : IExcelAddIn {
public void AutoClose() {
}
public void AutoOpen() {
IntelliSenseServer.Register();
}
}
}
and then (and this is just taken from the github page), you just need to use the ExcelDNA annotations on your functions:
[ExcelFunction(Description = "A useful test function that adds two numbers, and returns the sum.")]
public static double AddThem(
[ExcelArgument(Name = "Augend", Description = "is the first number, to which will be added")]
double v1,
[ExcelArgument(Name = "Addend", Description = "is the second number that will be added")]
double v2)
{
return v1 + v2;
}
which are annotated using the ExcelDNA annotations, the intellisense server will pick up the argument names and descriptions.
There are examples for using it with just VBA too, but i'm not too into my VBA, so i don't use those parts.
Also you can use, this Macro to assign Descriptions to arguments and the UDF:
Private Sub RegisterMyFunction()
Application.MacroOptions _
Macro:="SampleFunction", _ '' Your UDF name
Description:="calculates a result based on provided inputs", _
Category:="My UDF Category", _ '' Or use numbers, a list in the link below
ArgumentDescriptions:=Array( _ '' One by each argument
"is the first argument. tell the user what it does", _
"is the second argument. tell the user what it does")
End Sub
Credits to Kendall and the original post here.
For the UDF Categories
I just create a "help" version of the function. Shows up right below the function in autocomplete - the user can select it instead in an adjacent cell for instructions.
Public Function Foo(param1 as range, param2 as string) As String
Foo = "Hello world"
End Function
Public Function Foo_Help() as String
Foo_Help = "The Foo function was designed to return the Foo value for a specified range a cells given a specified constant." & CHR(10) & "Parameters:" & CHR(10)
& " param1 as Range : Specifies the range of cells the Foo function should operate on." & CHR(10)
&" param2 as String : Specifies the constant the function should use to calculate Foo"
&" contact the Foo master at master#foo.com for more information."
END FUNCTION
The carriage returns improve readability with wordwrap on. 2 birds with one stone, now the function has some documentation.
#will's method is the best. Just add few lines about the details for the people didn't use ExcelDNA before like me.
Download Excel-DNA IntelliSense from https://github.com/Excel-DNA/IntelliSense/releases
There are two version, one is for 64, check your Excel version. For my case, I'm using 64 version.
Open Excel/Developer/Add-Ins/Browse and select ExcelDna.IntelliSense64.xll.
Insert a new sheet, change name to "IntelliSense", add function description, as https://github.com/Excel-DNA/IntelliSense/wiki/Getting-Started
Then enjoy! :)
Unfortunately there is no way to add Tooltips for UDF Arguments.
To extend Remou's reply you can find a fuller but more complex approach to descriptions for the Function Wizard at
http://www.jkp-ads.com/Articles/RegisterUDF00.asp
I tried #ScottK's approach, first as a side feature of my functional UDF, then as a standalone _Help suffix version when I ran into trouble (see below). In hindsight, the latter approach is better anyway--more obvious to a user attentive enough to see a tool tip, and it doesn't clutter up the functional code.
I figured if an inattentive user just typed the function name and closed the parentheses while he thought it over, help would appear and he would be on his way. But dumping a bunch of text into a single cell that I cannot format didn't seem like a good idea. Instead, When the function is entered in a cell with no arguments i.e.
= interpolateLinear()
or
= interpolateLinear_Help()
a msgBox opens with the help text. A msgBox is limited to ~1000 characters, maybe it's 1024. But that's enough (barely 8^/) for my overly tricked out interpolation function. If it's not, you can always open a user form and go to town.
The first time the message box opened, it looked like success. But there are a couple of problems. First of course, the user has to know to enter the function with no arguments (+1 for the _Help suffix UDF).
The big problem is, the msgBox reopens several times in succession, spontaneously while working in unrelated parts of the workbook. Needless to say, it's very annoying. Sometimes it goes on until I get a circular reference warning. Go figure. If a UDF could change the cell formula, I would have done that to shut it up.
I don't know why Excel feels the need recalculate the formula over and over; neither the _Help standalone, nor the full up version (in help mode) has precedents or dependents. There's not an application.volatile statement anywhere. Of course the function returns a value to the calling cell. Maybe that triggers the recalc? But that's what UDFs do. I don't think you can not return a value.
Since you can't modify a worksheet formula from a UDF, I tried to return a specific string --a value --to the calling cell (the only one you can change the value of from a UDF), figuring I would inspect the cell value using application.caller on the next cycle, spot my string, and know not to re-display the help message. Seemed like a good idea at the time--didn't work. Maybe I did something stupid in my sleep-deprived state. I still like the idea. I'll update this when (if) I fix the problem. My quick fix was to add a line on the help box: "Seek help only in an emergency. Delete the offending formula to end the misery.
In the meantime, I tried the Application.MacroOptions approach. Pretty easy, and it looks professional. Just one problem to work out. I'll post a separate answer on that approach later.
A lot of dancing around the answer. You can add the UDF context help, but you have to export the Module and edit the contents in a text editor, then re-import it to VBA. Here's the example from Chip Pearson: Adding Code Attributes
I meet a problem which is probably very simple when I use a VBA function into a formula of a cell, I get the cell content "#NAME" (not found function ? while a macro using the function (for test) is executed normally (displays the wished content for the cell, the returned value by the function, which extracts the filename from a fullpath).
context :
I had by the past (more than 12 years ago) developed, may be 50,000, VBA instructions, using office2003.
Today I have to develop again some macros with Office365. So I have forgotten a lot since this time and some features can have changed which can become tricking (I need to read again my old soft to recall all my knowledge, but I have no access to for now)
The problem
I get the error "#name" when I use a function created into VBA
associated to the current workbook. No explanation, no help, I tried to
find something during several hours and I found nothing.
I have developed too for testing (see code) a "sub" which calls the function, and his execution is successful, but...
I cannot run the function from the formula of any cell.
I have tested the security parameters of macro and fully unlocked the execution temporarily, and too declare the local directory as confident area.
Note : this code is detailed as an example
The code
Public Function FNameOf(CellPointed As Range)
Dim CurCell As Range
Dim Text1 As String
Dim Text2 As String
Set CurCell = CellPointed
Text1 = CurCell.Value
Text2 = Mid$(Text1, InStrRev(Text1, "\") + 1, Len(Text1))
FNameOf = Text2
End Function
Sub DispFileName2()
Dim style, disp, titre
Dim Cursel As Range
'Cursel = ActiveCell
disp = FNameOf(ActiveCell)
style = vbOKOnly
titre = "Nom du fichier extrait du texte (fullpath) de la cellule courante"
MsgBox disp, style, titre
End Sub
If I submit the macro DispFileName2 if get the message with the file name extracted from the path which is the content of the current cell
If I set the formule of a cell :
=FNameOf(AnotherCell) 'which contains a fullpath to a file
I get always the error "#NOM" (in French version) or, I think so, "#NAME" (in english Version) as if the function name (ref) was unknown from the workbook (the code is not reached, a stop is set on the first instruction)
What can be the reason ?
Please place your user defined function somewhere in a module (neither in "ThisWorkbook" nor in the individual worksheet's code, e. g. "Feuil1").
You should add the result declaration As String also.
I understood the example is for reference only, but you may shorten it:
Public Function FNameOf(CellPointed As Range) As String
FNameOf = Mid(CellPointed.Value, InStrRev(CellPointed.Value, "\") + 1)
End Function
I just got the solution while reading in more details previous edited threads in several tabs.
It is explained into a remark of : thread 12351339
The text is :
Microsoft Excel Objects such as 'Sheet1' or 'ThisWorkbook' are
classes. I don't believe you can access Functions which you put in
these classes through a cell. You could access them in VBA e.g.
ThisWorkbook.Square2() but it's recommended to put all UDF's into as
standard module and not a worksheet module. – Eddie Sep 28 '17 at
13:49
By default the creation panel defines code associated to current worksheet, then the function is not visible for the worksheet while the sub is a macro of the worksheet.
I have created a module and the function has run immediately.
Best regards
Trebly
Note : I never met this problem of visibility before because the developments where since the beginning concerning VBA user classes and modules combining multiple Excel workbooks and Word and a Mail manager activeX and so on...
I keep the subject because of the explanations, code and keywords may be to find more easily the solution for anybody else.
First post so I'll try my best to make it a good one (please tell me if I'm doing it wrong).I can't seem to write the code properly to change the value of a check box or option button on a sheet using a variable.
Suppose the name of the check box name is "Chk1", normally I would write :
Worksheets("AP-1").Chk1.value=X
Where X is (either True or False). Since it is a Loop, I use a range variable called FoundRange and it's value is the name of the check box, so I tried:
dim chkname as string
chkname=foundrange.value
Worksheets("AP-1").Chkname.value=X
I also tried
Worksheets("AP-1").CheckBoxes(chkname).Value = X
and
Worsheets("AP-1").Shapes(chkname).ControlFormat.Value=X
I also had a linked cell that I used to change the value, but when it writes either false or true in it, the check box becomes gray and I need to press F2+Enter in the linked cell to make the check box show the proper value. I also tried to select the linked cell after changing its value and use that code:
Application.SendKeys "{F2}"
Application.SendKeys "{ENTER}"
but it did not work.
Please help me :)
Based on your initial code, it must be an ActiveX control, not a Form one, so:
dim chkname as string
chkname=foundrange.value
Worksheets("AP-1").OLEObjects(Chkname).Object.value = X
In Excel 2007, how do I add a description and parameter hints to a user-defined function? When I start typing a function invocation for a built-in function, Excel shows a description and parameter list--a tooltip. I'd like to do the same for the functions I define.
Not just for the formula insert wizard, but in the formula box, so if I key "=myFun(", at the "(" the tooltip pops up just like it does for "=average("
There's no help in VBA Help, none on MSDN and none on any of the Excel and VBA dedicated forums I can find, so this is clearly a long shot.
Not a tooltip solution but an adequate workaround:
Start typing the UDF =MyUDF( then press CTRL + Shift + A and your function parameters will be displayed. So long as those parameters have meaningful names you at-least have a viable prompt
For example, this:
=MyUDF( + CTRL + Shift + A
Turns into this:
=MyUDF(sPath, sFileName)
Professional Excel Development by
Stephen Bullen describes how to
register UDFs, which allows a
description to appear in the Function
Arguments dialog:
Function IFERROR(ByRef ToEvaluate As Variant, ByRef Default As Variant) As Variant
If IsError(ToEvaluate) Then
IFERROR = Default
Else
IFERROR = ToEvaluate
End If
End Function
Sub RegisterUDF()
Dim s As String
s = "Provides a shortcut replacement for the common worksheet construct" & vbLf _
& "IF(ISERROR(<expression>), <default>, <expression>)"
Application.MacroOptions macro:="IFERROR", Description:=s, Category:=9
End Sub
Sub UnregisterUDF()
Application.MacroOptions Macro:="IFERROR", Description:=Empty, Category:=Empty
End Sub
From: http://www.ozgrid.com/forum/showthread.php?t=78123&page=1
To show the Function Arguments dialog, type the function name and press CtrlA. Alternatively, click the "fx" symbol in the formula bar:
I know you've accepted an answer for this, but there's now a solution that lets you get an intellisense style completion box pop up like for the other excel functions, via an Excel-DNA add in, or by registering an intellisense server inside your own add in. See here.
Now, i prefer the C# way of doing it - it's much simpler, as inside Excel-DNA, any class that implements IExcelAddin is picked up by the addin framework and has AutoOpen() and AutoClose() run when you open/close the add in. So you just need this:
namespace MyNameSpace {
public class Intellisense : IExcelAddIn {
public void AutoClose() {
}
public void AutoOpen() {
IntelliSenseServer.Register();
}
}
}
and then (and this is just taken from the github page), you just need to use the ExcelDNA annotations on your functions:
[ExcelFunction(Description = "A useful test function that adds two numbers, and returns the sum.")]
public static double AddThem(
[ExcelArgument(Name = "Augend", Description = "is the first number, to which will be added")]
double v1,
[ExcelArgument(Name = "Addend", Description = "is the second number that will be added")]
double v2)
{
return v1 + v2;
}
which are annotated using the ExcelDNA annotations, the intellisense server will pick up the argument names and descriptions.
There are examples for using it with just VBA too, but i'm not too into my VBA, so i don't use those parts.
Also you can use, this Macro to assign Descriptions to arguments and the UDF:
Private Sub RegisterMyFunction()
Application.MacroOptions _
Macro:="SampleFunction", _ '' Your UDF name
Description:="calculates a result based on provided inputs", _
Category:="My UDF Category", _ '' Or use numbers, a list in the link below
ArgumentDescriptions:=Array( _ '' One by each argument
"is the first argument. tell the user what it does", _
"is the second argument. tell the user what it does")
End Sub
Credits to Kendall and the original post here.
For the UDF Categories
I just create a "help" version of the function. Shows up right below the function in autocomplete - the user can select it instead in an adjacent cell for instructions.
Public Function Foo(param1 as range, param2 as string) As String
Foo = "Hello world"
End Function
Public Function Foo_Help() as String
Foo_Help = "The Foo function was designed to return the Foo value for a specified range a cells given a specified constant." & CHR(10) & "Parameters:" & CHR(10)
& " param1 as Range : Specifies the range of cells the Foo function should operate on." & CHR(10)
&" param2 as String : Specifies the constant the function should use to calculate Foo"
&" contact the Foo master at master#foo.com for more information."
END FUNCTION
The carriage returns improve readability with wordwrap on. 2 birds with one stone, now the function has some documentation.
#will's method is the best. Just add few lines about the details for the people didn't use ExcelDNA before like me.
Download Excel-DNA IntelliSense from https://github.com/Excel-DNA/IntelliSense/releases
There are two version, one is for 64, check your Excel version. For my case, I'm using 64 version.
Open Excel/Developer/Add-Ins/Browse and select ExcelDna.IntelliSense64.xll.
Insert a new sheet, change name to "IntelliSense", add function description, as https://github.com/Excel-DNA/IntelliSense/wiki/Getting-Started
Then enjoy! :)
Unfortunately there is no way to add Tooltips for UDF Arguments.
To extend Remou's reply you can find a fuller but more complex approach to descriptions for the Function Wizard at
http://www.jkp-ads.com/Articles/RegisterUDF00.asp
I tried #ScottK's approach, first as a side feature of my functional UDF, then as a standalone _Help suffix version when I ran into trouble (see below). In hindsight, the latter approach is better anyway--more obvious to a user attentive enough to see a tool tip, and it doesn't clutter up the functional code.
I figured if an inattentive user just typed the function name and closed the parentheses while he thought it over, help would appear and he would be on his way. But dumping a bunch of text into a single cell that I cannot format didn't seem like a good idea. Instead, When the function is entered in a cell with no arguments i.e.
= interpolateLinear()
or
= interpolateLinear_Help()
a msgBox opens with the help text. A msgBox is limited to ~1000 characters, maybe it's 1024. But that's enough (barely 8^/) for my overly tricked out interpolation function. If it's not, you can always open a user form and go to town.
The first time the message box opened, it looked like success. But there are a couple of problems. First of course, the user has to know to enter the function with no arguments (+1 for the _Help suffix UDF).
The big problem is, the msgBox reopens several times in succession, spontaneously while working in unrelated parts of the workbook. Needless to say, it's very annoying. Sometimes it goes on until I get a circular reference warning. Go figure. If a UDF could change the cell formula, I would have done that to shut it up.
I don't know why Excel feels the need recalculate the formula over and over; neither the _Help standalone, nor the full up version (in help mode) has precedents or dependents. There's not an application.volatile statement anywhere. Of course the function returns a value to the calling cell. Maybe that triggers the recalc? But that's what UDFs do. I don't think you can not return a value.
Since you can't modify a worksheet formula from a UDF, I tried to return a specific string --a value --to the calling cell (the only one you can change the value of from a UDF), figuring I would inspect the cell value using application.caller on the next cycle, spot my string, and know not to re-display the help message. Seemed like a good idea at the time--didn't work. Maybe I did something stupid in my sleep-deprived state. I still like the idea. I'll update this when (if) I fix the problem. My quick fix was to add a line on the help box: "Seek help only in an emergency. Delete the offending formula to end the misery.
In the meantime, I tried the Application.MacroOptions approach. Pretty easy, and it looks professional. Just one problem to work out. I'll post a separate answer on that approach later.
A lot of dancing around the answer. You can add the UDF context help, but you have to export the Module and edit the contents in a text editor, then re-import it to VBA. Here's the example from Chip Pearson: Adding Code Attributes
In Excel 2007, how do I add a description and parameter hints to a user-defined function? When I start typing a function invocation for a built-in function, Excel shows a description and parameter list--a tooltip. I'd like to do the same for the functions I define.
Not just for the formula insert wizard, but in the formula box, so if I key "=myFun(", at the "(" the tooltip pops up just like it does for "=average("
There's no help in VBA Help, none on MSDN and none on any of the Excel and VBA dedicated forums I can find, so this is clearly a long shot.
Not a tooltip solution but an adequate workaround:
Start typing the UDF =MyUDF( then press CTRL + Shift + A and your function parameters will be displayed. So long as those parameters have meaningful names you at-least have a viable prompt
For example, this:
=MyUDF( + CTRL + Shift + A
Turns into this:
=MyUDF(sPath, sFileName)
Professional Excel Development by
Stephen Bullen describes how to
register UDFs, which allows a
description to appear in the Function
Arguments dialog:
Function IFERROR(ByRef ToEvaluate As Variant, ByRef Default As Variant) As Variant
If IsError(ToEvaluate) Then
IFERROR = Default
Else
IFERROR = ToEvaluate
End If
End Function
Sub RegisterUDF()
Dim s As String
s = "Provides a shortcut replacement for the common worksheet construct" & vbLf _
& "IF(ISERROR(<expression>), <default>, <expression>)"
Application.MacroOptions macro:="IFERROR", Description:=s, Category:=9
End Sub
Sub UnregisterUDF()
Application.MacroOptions Macro:="IFERROR", Description:=Empty, Category:=Empty
End Sub
From: http://www.ozgrid.com/forum/showthread.php?t=78123&page=1
To show the Function Arguments dialog, type the function name and press CtrlA. Alternatively, click the "fx" symbol in the formula bar:
I know you've accepted an answer for this, but there's now a solution that lets you get an intellisense style completion box pop up like for the other excel functions, via an Excel-DNA add in, or by registering an intellisense server inside your own add in. See here.
Now, i prefer the C# way of doing it - it's much simpler, as inside Excel-DNA, any class that implements IExcelAddin is picked up by the addin framework and has AutoOpen() and AutoClose() run when you open/close the add in. So you just need this:
namespace MyNameSpace {
public class Intellisense : IExcelAddIn {
public void AutoClose() {
}
public void AutoOpen() {
IntelliSenseServer.Register();
}
}
}
and then (and this is just taken from the github page), you just need to use the ExcelDNA annotations on your functions:
[ExcelFunction(Description = "A useful test function that adds two numbers, and returns the sum.")]
public static double AddThem(
[ExcelArgument(Name = "Augend", Description = "is the first number, to which will be added")]
double v1,
[ExcelArgument(Name = "Addend", Description = "is the second number that will be added")]
double v2)
{
return v1 + v2;
}
which are annotated using the ExcelDNA annotations, the intellisense server will pick up the argument names and descriptions.
There are examples for using it with just VBA too, but i'm not too into my VBA, so i don't use those parts.
Also you can use, this Macro to assign Descriptions to arguments and the UDF:
Private Sub RegisterMyFunction()
Application.MacroOptions _
Macro:="SampleFunction", _ '' Your UDF name
Description:="calculates a result based on provided inputs", _
Category:="My UDF Category", _ '' Or use numbers, a list in the link below
ArgumentDescriptions:=Array( _ '' One by each argument
"is the first argument. tell the user what it does", _
"is the second argument. tell the user what it does")
End Sub
Credits to Kendall and the original post here.
For the UDF Categories
I just create a "help" version of the function. Shows up right below the function in autocomplete - the user can select it instead in an adjacent cell for instructions.
Public Function Foo(param1 as range, param2 as string) As String
Foo = "Hello world"
End Function
Public Function Foo_Help() as String
Foo_Help = "The Foo function was designed to return the Foo value for a specified range a cells given a specified constant." & CHR(10) & "Parameters:" & CHR(10)
& " param1 as Range : Specifies the range of cells the Foo function should operate on." & CHR(10)
&" param2 as String : Specifies the constant the function should use to calculate Foo"
&" contact the Foo master at master#foo.com for more information."
END FUNCTION
The carriage returns improve readability with wordwrap on. 2 birds with one stone, now the function has some documentation.
#will's method is the best. Just add few lines about the details for the people didn't use ExcelDNA before like me.
Download Excel-DNA IntelliSense from https://github.com/Excel-DNA/IntelliSense/releases
There are two version, one is for 64, check your Excel version. For my case, I'm using 64 version.
Open Excel/Developer/Add-Ins/Browse and select ExcelDna.IntelliSense64.xll.
Insert a new sheet, change name to "IntelliSense", add function description, as https://github.com/Excel-DNA/IntelliSense/wiki/Getting-Started
Then enjoy! :)
Unfortunately there is no way to add Tooltips for UDF Arguments.
To extend Remou's reply you can find a fuller but more complex approach to descriptions for the Function Wizard at
http://www.jkp-ads.com/Articles/RegisterUDF00.asp
I tried #ScottK's approach, first as a side feature of my functional UDF, then as a standalone _Help suffix version when I ran into trouble (see below). In hindsight, the latter approach is better anyway--more obvious to a user attentive enough to see a tool tip, and it doesn't clutter up the functional code.
I figured if an inattentive user just typed the function name and closed the parentheses while he thought it over, help would appear and he would be on his way. But dumping a bunch of text into a single cell that I cannot format didn't seem like a good idea. Instead, When the function is entered in a cell with no arguments i.e.
= interpolateLinear()
or
= interpolateLinear_Help()
a msgBox opens with the help text. A msgBox is limited to ~1000 characters, maybe it's 1024. But that's enough (barely 8^/) for my overly tricked out interpolation function. If it's not, you can always open a user form and go to town.
The first time the message box opened, it looked like success. But there are a couple of problems. First of course, the user has to know to enter the function with no arguments (+1 for the _Help suffix UDF).
The big problem is, the msgBox reopens several times in succession, spontaneously while working in unrelated parts of the workbook. Needless to say, it's very annoying. Sometimes it goes on until I get a circular reference warning. Go figure. If a UDF could change the cell formula, I would have done that to shut it up.
I don't know why Excel feels the need recalculate the formula over and over; neither the _Help standalone, nor the full up version (in help mode) has precedents or dependents. There's not an application.volatile statement anywhere. Of course the function returns a value to the calling cell. Maybe that triggers the recalc? But that's what UDFs do. I don't think you can not return a value.
Since you can't modify a worksheet formula from a UDF, I tried to return a specific string --a value --to the calling cell (the only one you can change the value of from a UDF), figuring I would inspect the cell value using application.caller on the next cycle, spot my string, and know not to re-display the help message. Seemed like a good idea at the time--didn't work. Maybe I did something stupid in my sleep-deprived state. I still like the idea. I'll update this when (if) I fix the problem. My quick fix was to add a line on the help box: "Seek help only in an emergency. Delete the offending formula to end the misery.
In the meantime, I tried the Application.MacroOptions approach. Pretty easy, and it looks professional. Just one problem to work out. I'll post a separate answer on that approach later.
A lot of dancing around the answer. You can add the UDF context help, but you have to export the Module and edit the contents in a text editor, then re-import it to VBA. Here's the example from Chip Pearson: Adding Code Attributes