User logs into multiple stations at once

you can via Group Policy specify which computer they can log onto. Then they can only log on to that one computer.

The user should be able to login to different stations - depending upon what station is open when they come into the office -

What I am trying to do however is make it so that a user is unable to login to more than 1 station at a time.

There should be an option in the user settings on the server to limit one log in at a time or limit the number of simultaneous logins. This would be on the server end and it doesn't say what machines they can log in on.

Please view the following informational page:
http://bink.nu/DesktopModules/ArticleDetail.aspx?ArticleID=1452 (remove any spaces)
It describes an add-on from Microsoft called LimitLogon. Although not officially supported, it is available from Microsoft.

Have a talk with the person. That usually works. If not, assign computers and create a local account for everyone on the computer you assigned to them.