How to Block AIM Express.

We’ve recently put a no Instant messanger policy on the books and blocked IM ports and IP at the firewall level. However, AOL now has AIM Express which allows instant messenging by-passing port 5190. Does anyone know how to block this? I believe all I would have to do is block access to the site, but I only know how to block access to the IP address.

Please help. The AIM Express address is http://www.aol.com/aim/aimexpress.html.

Please feel free to email me at jmerulla@cwcainc.com
Thanks a bunch