I'm in the process of converting to Excel 2010, and have created an add-in that works with a couple of workbooks. This all works fine under Win7 Excel2010, however it also needs to run on WinXP, Excel 2003 with compatability pack. This is where the fun starts. I have created new .xlsm files on W7/10 and copied them to an XP/03C machine. Saved the macro loaded workbook lets say MacroBook.xla (VBAProject=MacroBook, so Project Explorer reads "MacroBook(MacroBook)") as a .xla and created references in a couple of the books, lets say Book1.xlsm and Book2.xlsm, on initial opening it works fine and macros fire as expected. Once the books have been saved and excel has been closed I open them again and now the vbaproject name of the MacroBook.xla change to the first workbook opened, the Project explorer reads "MacroBook(Book1)" or if Book2 was opened first, "MacroBook(Book2), has anyone out there any idea what is going on/ what I'm doing wrong?