Limiting time on computer

Hi all,

I am setting up a domain W2K server at a camp that is allowing campers to use some computers to read emails and surf the web.

The issue is that some campers tend to hog the computers going for hours without stop.

We need to set up some way that limits when and for how long a session can last. I have checked the literature and determined that group policy can limit when someone can log on, but not for how long they can stay on.

Is there something or some way I can do this?

thanks

Nate