Setting Range.Formula with custom function

Hi all,

I recently set up some functions based on Chip Pearson's tutorial for referencing worksheets from Formulas. (http://www.cpearson.com/excel/sheetref.htm)

The problem I'm now having is that I can't use VBA to set these functions in place; it returns a syntax error.

For example, I want I37 on most sheets to have the same formula. So I have the following:

For Each Worksheet In Worksheets

Select Case Worksheet.Index

Case 1, 2, 3
'Do Nothing

Case Else
'The below returns a syntax error (highlighted in red)
Worksheets(Worksheet.Index).Range("I37").Formula = "=RefOnPrevSheet("I39"))"

End Select

Next Worksheet

When I type the formula directly in the cell, and debug.print it, it shows exactly what I've put in quotes. How can I put this formula into my cells without returning a syntax error?

Cheers,

Bob