[lug] access and time length control

[Phil Rasch]

I have a couple of teenage kids. I would like to limit access to a linux box 
using a rule like the following.

"Let Bobby login between 8PM and 10PM for at most one hour on
weekdays, and between 8AM and midnight for at most two hours per day
on weekends and holidays"

I know I can do parts of this task using squid, but I can think of a couple 
of problems with that approach. 
1) it doesnt prevent the kids doing games on the box. Just getting on the net.
2) if one makes a connection (for example with GAIM) prior to the "end time" 
   they can keep it going forever unless I figure out some smart way to 
   force a restart of the connection.

I really dont want to spend a week figuring out a fancy way to do this. Does
anybody have any simple suggestions?

Thanks

Phil