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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 need help to change the following function into VBA code. This will be part of a larger code.
IF((WEEKDAY($B12)=7),$I12,"")
There are probably more than 5 ways to do what you want, depending on what exactly do you need. One of these ways is to build a simple custom formula like this:
Public Function changingIfAndWeekday() As Variant
Application.Volatile
If Weekday(Range("B12")) = 7 Then
changingIfAndWeekday = Range("I12")
Else
changingIfAndWeekday = ""
End If
End Function
You could also do it like so (if you want the result on cell C12):
Sheet1.range("C12").value = "=IF(Weekday(Sheet1.range("B12").value = 7),Sheet1.range("I12").value,"")
You could also do it like so (if you want the result on a variable):
Variable = "=IF(Weekday(Sheet1.range("B12").value = 7),Sheet1.range("I12").value,"")
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've use my Excel 2013 to record a macro in inserting a chart, a column-clustered chart in my case. In the view code option, it shows me a line of code as below:
ActiveSheet.Shapes.Addchart2(286,xl3DColumnClustered).Select
Please help me as I cannot understand what does the number 286 represent. I know the syntax of Addchart2 is:
expression.AddChart2(Style,XlChartType,Left,Top,Width,Height,NewLayout)
If I change the "286" to "285", the chart appears with a blue background. An error comes out if the number is 100.
Can anyone kindly tell me what does the number represent?
One can also provide only the ChartType and the application will use the default style.
Set oShp = ActiveSheet.Shapes.AddChart2(XlChartType:=xl3DColumnClustered)
oShp.Chart.SetSourceData Source:=RngDta
This picture shows the default ChartStyle for all ChartTypes (excluding StockHLC and StockVOHLC)
This won't directly answer your question, but it will help you figure out what is going on.
This is pure conjecture on my part, but I would guess it's an undocumented bitfield. As you may know a bit field is just a way to use a number. So image we have a Byte variable which can be 8 bits (or flags). So in a byte we can store up to 8 values.
Example: We have field called "DaysOpen" bits 1-7 mean the store is open on that day of the week. (We'll ignore the 8th bit.) So if the store is open M-F that would be binary 0111 1100.
Then you just convert that number to decimal and we see that it's 124.
That variable is a Variant so it could be anything from a Byte to Long meaning it could be storing up to 64 different flags.
As a side note (if you are interested) you can use bit fields like so:
Option Explicit
Public Enum DayFlags
'Notice these are power of 2.
dfSunday = 1
dfMonday = 2
dfTuesday = 4
dfWednesday = 8
dfThursday = 16
dfFriday = 32
dfSaturday = 64
End Enum
Sub Example()
Dim openHours As DayFlags
'Set the flags:
openHours = dfMonday Or dfTuesday Or dfThursday
'See the binary?
MsgBox Right$("00000000" & Excel.WorksheetFunction.Dec2Bin(openHours), 8)
'Notice the order is right to left. This is call endianness.
'You can check for a specific flag like this:
MsgBox IsOpenOnDay(openHours, dfMonday) & vbNewLine & IsOpenOnDay(openHours, dfFriday)
'You can add a flag like this:
openHours = openHours Or dfFriday
MsgBox IsOpenOnDay(openHours, dfMonday) & vbNewLine & IsOpenOnDay(openHours, dfFriday)
'You can remove a flag like this:
openHours = openHours Xor dfFriday
MsgBox IsOpenOnDay(openHours, dfMonday) & vbNewLine & IsOpenOnDay(openHours, dfFriday)
End Sub
Private Function IsOpenOnDay(ByVal openHours As DayFlags, ByVal day As DayFlags) As Boolean
IsOpenOnDay = ((openHours And day) = day)
End Function
Well , I had the same situation once, and those are basically chart styles. I tried to figure out the exact numbering but then i realized that recording was a much easier way of knowing the style numbers just as you have done here.
To answer you question, record macros to know which style you want to implement in your macros.
Just checking to see if 5 years later anyone has a better answer. I sure could use an enumeration of the chart styles; I don't like putting simple numbers in my code without some explanation as to what it means. Of course, I could use a comment, but if the numbers are documented, then that means they could change.
I found a partial list: https://learn.microsoft.com/en-us/office/vba/api/excel.xlcharttype
I'm sure these numbers, plus the bitfield variations as suggested by Pillgram above to control various other chart aspects, answer the question. The possible combinations are in the thousands, so a full list would be pretty useless. Recording is still your best bet.
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