VBA - Update Other Cells via User-Defined Function

Question

I have a UDF(User-Defined Function) in VBA that needs to modify cell range on Excel.

Since a UDF cannot do this, I tried using Event calls.

When I raise a Custom Event and try to write to cells, I get #Value error. On the other hand, Application events such as Private Sub App_SheetChange(ByVal Sh As Object, ByVal Target As Range) can write to cells.

My questions is how do I update other cells by calling a UDF?

Answer 1

Here is a way you can circumvent the restraint, you must do it indirectly. Method copied from Excel - How to fill cells from User Defined Function?:

In a standard module:

Public triggger As Boolean
Public carryover As Variant
Function reallysimple(r As Range) As Variant
    triggger = True
    reallysimple = r.Value
    carryover = r.Value / 99
End Function

In worksheet code:

Private Sub Worksheet_Calculate()
    If Not triggger Then Exit Sub
    triggger = False
    Range("C1").Value = carryover
End Sub

This could be expanded for your purposes. Essentially, the UDF updates public variables which are then read from the Worksheet_Calculate event to do... anything you like.

Another more complicated approach would be to write a vbscript file from your function that will attempt to automate Excel and run it via Shell. However, the method I listed above is much more reliable.