Thanks for the reply.

I've set Excel to allow all macros, this doesn't correct the problem.

The add-in was what I expected it to be also. I attempted to access terminal
services (office 2003) and using a similar file path, locate the add-in which
I had presumed was with the other add-in files under...

C:\Program Files\Microsoft Office\OFFICE11\Library

The pcas97.xla file wasn't there (even checked hidden files, and checked the
folders in the Library directory). I also checked in the ADDINS folder in the
OFFICE11 directory.

I believe the file may have been created by the originator of the
spreadsheet who is the external party mailing this to us.

I still don't understand how it can work on Office 2003 when i'm unable to
find the add-in where Office 2007 says it should be.