Block user settings in a GPO to a group of computers

I have a user GPO for windows redirection of Desktop folders and such. I need to exclude a group of computers (they are all in a security group). All of hte articles i find is adding a user policy to a workstation and i need to find a way to block the user settings from applying to the workstation.

This is why:

we have branch computers where our users log onto the physical systems and then launch Citrix desktop to do their work. We have discoved that they redirection is slowing down the workstations and the users only need the redirection once they are in Citrix.

Thanks for any help.