[squid-users] Bumping users from website

Dear List,

I've created ACL's in squid to keep my users from going to certain
websites during certain parts of the day. The acl's are working just
fine. But is there a way to kick those same users off of these acl
restricted sites if they already happen to be on the site when the acl
kicks in? Let's say the the acl restricts users from visiting a
particular website from 4PM-6PM. If the users are already on the site
at 3:59PM, once 4PM hits, so far they're still able to browse the site.
Of course once they leave the site they can't get back in though until
after 6PM.

Thanks,

David