How can I forward Port 80 to our web server using Routing & Remote Access?

I just finished setting up a dedicated windows 2003 web server on our network and I'm trying to figure out how to configure the Routing in Routing & Remote Access in SBS08. I want to forward port 80 to the web server. There is no router between the cable modem and the server. The 08 server is the dhcp server and the firewall.

Thanks,
MN