>I had the function at the top of the program - sorry about that.
>
>However, I get an error on this line:
>tcWindowName = Lower(tcWindowName)
>Error: Function argument value, type, or count is invalid.
>
>Since the current Form (form A) is a form set - could that have something to do with the error?

lower() operates on character values. As error message says tcWindowName is not a string. Place this before that line to check (or suspend and invoke debugger what tcWindowName is) :

messagebox(type('tcWindowName')+'/'+trans(tcWindowName))

Cetin