Writing to a worksheet from a VBA function - excel

Question

I am trying to write some intermediate results in a user defined VBA function to a worksheet. I have tested the function, and it works correctly. I am aware that I cannot modify / write to cells from a UDF, so I tried passing the relevant results to a subroutine which I hoped would then be able to write to the spreadsheet.
Unfortunately my scheme doesn't work, and I am trying to think through this problem.
Public Function f(param1, param2)
result = param1 * param2
call writeToSheet(result)
f = param1 + param2
end
public sub writeToSheet(x)
dim c as range
c = range("A1")
c.value = x
end
I would like to see the product of param1 and param2 in cell A1. Unfortunately, it does not happen - the subroutine just ends abruptly as soon as it attempts to execute the first statement (c = range("A1") ). What am I doing wrong, and how can I fix it?
If it is simply impossible to write to a spreadsheet in this way, is there some other way in which to store intermediate results for later review? My real life problem is a little more complicated that my stylized version above, as I generate a new set of intermediate results each time I go through a loop, and want to store them all for review.

Answer 1

This idea might work for you. The function ParamProduct calls SetProps which writes both parameters to custom document properties (View from File > Properties > Advanced Properties > Custom). Call the function with =ParamProduct(A1, A2) or =ParamProduct(123, 321)
Function ParamProduct(Param1 As Variant, _
Param2 As Variant) As Double
Dim Fun As Double
Dim Param As Variant
Dim i As Integer
Param = Param1
For i = 1 To 2
SetProp "Param" & i, Param
Param = Param2
Next i
ParamProduct = Param1 + Param2
End Function
Private Sub SetProp(Pname As String, _
PropVal As Variant)
' assign PropVal to document Property(Pname)
' create a custom property if it doesn't exist
Dim Pp As DocumentProperty
Dim Typ As MsoDocProperties
If IsNumeric(PropVal) Then
Typ = msoPropertyTypeNumber
Else
Select Case VarType(PropVal)
Case vbDate
Typ = msoPropertyTypeDate
Case vbBoolean
Typ = msoPropertyTypeBoolean
Case Else
Typ = msoPropertyTypeString
End Select
End If
On Error Resume Next
With ThisWorkbook
Set Pp = .CustomDocumentProperties(Pname)
If Err.Number Then
.CustomDocumentProperties.Add Name:=Pname, LinkToContent:=False, _
Type:=Typ, Value:=PropVal
Else
With Pp
If .Type <> Typ Then .Type = Typ
.Value = PropVal
End With
End If
End With
End Sub
Use this UDF to recall the properties to the worksheet.
Function GetParam(ByVal Param As String) As Variant
GetParam = Propty(Param)
End Function
Private Function Propty(Pname As String) As Variant
' SSY 050 ++
' return null string if property doesn't exist
Dim Fun As Variant
Dim Pp As DocumentProperty
On Error Resume Next
Set Pp = ThisWorkbook.CustomDocumentProperties(Pname)
If Err.Number = 0 Then
Select Case Pp.Type
Case msoPropertyTypeNumber
Fun = CLng(Fun)
Case msoPropertyTypeDate
Fun = CDate(Fun)
Case msoPropertyTypeBoolean
Fun = CBool(Fun)
Case Else
Fun = CStr(Fun)
End Select
Fun = Pp.Value
End If
The worksheet function below works (A6 has a value of "Param2")
=GetParam("Param1")*GetParam(A6)
The above code will create a property if it doesn't exist or change its value if it does. The sub below will delete an existing property and do nothing if it's called to delete a property that doesn't exist. You might call it from one of the above subs or functions.
Private Sub DelProp(ByVal Pname As String)
On Error Resume Next
ThisWorkbook.CustomDocumentProperties(Pname).Delete
Err.Clear
End Sub

Answer 2

Thanks a mill everyone. Printing to the immediate window is the easiest by far, but allowed me to print only a single item. I therefore concatenated all 5 items into a single string and printed it in the immediate window:
dummystr = CStr(slope1) & ", " & CStr(intercept1) & ", " & CStr(slope2) & ", " & CStr(intercept2) & ", " & CStr(sse(i))
Debug.Print dummystr