Joel wrote:

The original excel workbook extension is xls. Microsoft added an new
extension in 2007 whichis xlsm which is a workbook with macros. A older xls
workbook in 2007 needs to save the workbook as xlsm before the macro(s) will
work. A xls in 2007 has macros disabled. The xls and xlsm are binary files
which is in a custom format that microsoft developed

Thanks for the explanation. We're using Office 2003 and in the process
of discussing upgrading to 2007. It will occur, but when I can't say.
For all I know, maybe after another version of Office is released...or
maybe next month.