Herllo Derek,

I am a bit late but, I was researching stuff like this, so it could be useful to someone passing as I did a while back

I have not quite figured exactly what you (Derek)  want/ wanted  to do.

But I can give a very simple alternative coding to get a UDF to change other cells, directly in terms of simplicity, ( possibly very indirectly in terms of what is happening behind the scenes.: What is going on here is sometimes considered as VBA having some redirection and ended up a bit lost, or rather does not know where it came from ).

No guarantees, but it may be something for you or others to consider

_ First put all these codings in a normal module

 Option Explicit
' This is the main UDF, used by writing in a cell something of this form   =UDF_Where(E3:E5)
Function UDF_Where(ByVal Cels As Range) As String      ' Looking at this conventionally, a string is likely to be returned  by this function in the cell you put the UDF into
 Let UDF_Where = "This is cell " & ActiveCell.Address & ", where the UDF is in" ' Conventional use of UDF to change value of the cell that it is in
Worksheets("Derek").Evaluate Name:="OverProc(" & Cels.Address & ")"             ' Unconventional use of a UDF to change other cells    ' The  Evaluate(" ")  thing takes the syntax of  Excel spreadsheet   So I need this sort of thing
End Function


Sub OverProc(Cels As Range) ' This can be a  Sub  or  Function
Dim SteerCel As Range
    For Each SteerCel In Cels
     Let SteerCel = "This is cell " & SteerCel.Address & ", from the range I passed my UDF (" & Cels.Address & ")"
    Next SteerCel
 ActiveCell.Offset(10, 0) = "This cell is 10 rows down from where my UDF is"
End Sub

( You will need to name a worksheet "Derek"., (That is not a general requirement but just ties up with the demo coding above and  in the uploaded workbook) )

_ Now, In the worksheet named "Derek", type in any cell, for example D2, the following

=UDF_Where(E3:E5)

, then hit Enter

You should see these results

Alan

‘StackOverflowUDFChangeOtherCells.xls’  https://app.box.com/s/knpm51iolgr1pu3ek2j96rju8aifu4ow