how to Set default Workbook as .XLS for Bex 7.0

Dear Experts,

I have a customised default workbook set for Bex 7.0. The Extention of this Workbook is .XLSM

Currently it is not accessible using Excel 2003 due to format issue.

1)Kindly let me know what should be done so that I can open this Workbook in Excel 2003.

2) Suggest a way to set the default extension for Bex 7.0 "Custom" workbook (Not SAP standard, the option is available in Global settings-->Default workbook) to .XLS.

Thank you,

Nandita