Terminal Server Group Policy Problem

I have a 2K TS memeber server. I have a group policy to lock down the desktop settings dished out to the terminal server users. Some of the users also have 2K workstations and unfortuately if I add their user accounts to the TSUsers group (that is the group that has the locked down desktop) It is also affecting their local logon. The obvious workaround is to have one username for logging onto their workstation and one for the terminal server but I dont want to have to do that. How can I tell mygroup policy to only affect the user accounts only if they log onto a particluar machine (the TS)

Jody