Blocking AOL traffic with Dlink DIR 625 Router

Trying to block / turn off AOL instatnt messenger traffic via my router (to keep kids off...)

Dlink DIR 625 router.

I can't block specific ports - because the ports keep changing - correct ?

On this router, I cannot block a specific website - someone told me to below access to login.oscar.aol.com and that would do it - but I can't.

Any ideas ?

Thanks !