Sorry for the repost, but I could not get an anwer on the original and this
is still plaguing me.

I have an XLA with a User Defined Function in it. Upon loading I attempt to
load the function into a function category in Excel (UDF category 14). The
UDF is called "VowelCount". When Excel starts up and opens the XLA I get an
error message in the ThisWorkbook module:

"Run time Error 1004: Cannot edit a macro on a hidden workbook. Unhide the
workbook using the Unhide command"


The code is as follws:
Private Sub Workbook_Open()
Application.MacroOptions Macro:="VowelCount", Category:=14
End Sub


Why is this happening? The XLA is obviously hidden file. Do I have to
momentarily unihde it to add the function to the function category and then
hide it again?


Thanks