It should work fine in your Personal.xls workbook. It could have to
do with the code in the UDF. If you are referencing something like
ThisWorkbook, then it is trying to apply the UDF to the Personal.xls
workbook, which would be incorrect. Could you post up the UDF code?

Paige wrote:
I have a UDF that have tried to add to my Personal.xls, so it will be
available as needed. (It works fine if I put the code in a normal workbook.)
It is in a regular module in my Personal.xls VBA project. After researching
thought it had to do with needing to add a reference to Personal.xls; when I
try to do that via Tools/References/Browse and select Personal.xls it adds
'VBAProject' to the list of references with a checkmark, but then says that
the name conflicts with an existing module, project or object library and
removes it. Am confused about what I'm doing wrong here. Any advice please?