Floating Pool, Don't Take a Session

This might not make a lot of sense, but, asking anyway.

If we have a floating pool, say 500 desktops, and 500 unique users assigned, is there a way to make it so if user1 is already logged into desktop1, that if he walks somewhere else and tries to login again, he won't steal desktop1 from the previous session?

We have generic accounts setup for a floating pool, and the accounts are assigned to terminals. To help eliminate some human error, I'd love to make it so if the pool sees the account logged in somewhere else, he'll just reject the new session's attempt to use that same account.

This can be fixed by moving to 1 account and allowing the pool to spit our multiple sessions for a single account, but, we're not there yet.

Thanks in advance.