Modifying Exchange Objects in AD

I recently modified my 200 users by adding a value to the "Office" option within the account in AD. This is mainly because all of remote offices small and we needed some way to distiguish quickly who was where. Now, within the GAL, when you do a search for a user and the criteria also matches a value set for a users "Office" object, it also returns all these results. I need to get the GAL only search theough the display and alias objects and not the "Office" object. Any ideas? I assume I would need to modify and attribute within the AD using the schema admin, but finding it is proving impossible.