I changed the Excel XLSTART folder to a different location than the default (which was C:\Users\{My username}\AppData\Roaming\Microsoft\Excel\XLSTART) , and then deleted the default XLSTART folder. However whenever I start Excel, it creates an empty XLSTART folder at the default location. This in itself doesn't cause a problem.

I put a VB macro in PERSONAL.xlsb in the new XLSTART folder which adds a line to the right-click menu for all Excel workbooks.

The problem occurs when I click on the added line in any workbook. I get the message "Sorry, Excel can't open two workbooks with the same name at the same time."

What are the two workbooks with the same name? I have only one workbook open. I've done a search and the only PERSONAL.xlsb file found was the one in the new XLSTART folder I created.