Hide Menu On Opening - Unhide on Close

I want to open a *.xls file which, when opened, hides the 'Protection' option from the 'Tools' menu so that the users cannot unprotect(?) the workbook. (Dont want to use passwords due to other macros running in the spreadsheet.)

All my attemps have resulted in my MS Excel application being changed and not the individual file.

Any thoughts?

Thanks in advance ;o)