MS Office 2007: how do I lock users in default save path?

Dear all,

I have been having a problem and cannot find the answer on the Internet yet. I am trying to find a way to:
1. change the default save path for Office 2007 applications
2. lock users in this default path so they can only browse dówn the directory tree and not up.

I succeeded at doing 1: I use the Group Policy Management Console to change the Group Policy Objects. This works. The default save path is set.

2. remains a mystery however. So my question remains: is it possible to lock the user in the default save path in MS Office (and in MS Office only)? So; when a user hit Save (As) the window should open in the default folder and the user should not be able to browse up...If possible, how do I tackle this?

Thanks a million in advance...