instead of a field with '1', have a field that is set to the time and date the ban expires. then everytime they try to login compare the current date/time to the expire date and time to see if it is after the expire date. If not you could display a nifty little message like 'You are currently banned, please try again at 2001-06-05 7:30.' or something like that, if you want.
If they are not banned make the expire something like '0000-00-00 00:00'
You can do all of that through the date function.
This is one way to do it. You could also have a seperate table for bans and do just about the same thing.
Either way will work.
Just some thoughts.
