I do not understand what you are trying to do. Try explaining WHAT you are trying to do not HOW you are trying to do it. The how approach you are taking sounds wrong and mixing the how in with the what makes understanding your issue difficult. The only what I can see is
Quote Originally Posted by johncraw View Post
In the future we want only computer club members or "guests" use the computers.
If you only want certain users to use the computers then only give them the password. If the groups of users change then change the password. Solved.