Filtering port 443

In an educational environment, we are using key word blocking on the firewall for specific Web sites, and generally improper locations.

Does anyone have a possible solution that will allow me to block port 443 for specific sites such as vtunnel, meebo, and kproxy, but still allow access for other sites that use this port?

We are running Windows XP pro on the workstations and Windows 2000 Advanced Server in conjunction with a Netgear VPN Firewall.

Thanks!