Netopia R910 with block of ip's

I have a Netopia R910 that was previously setup to use a dhcp based cable account. We had an internal requirement for a static IP address and were provided with a block of IP's (5 to be exact). The problem is that the requirement was for a second web server to be setup behind the firewall. We already have 443/tcp and 80/tcp mapped to our exchange server for remote email access but also require 443/ tcp and 80/tcp to be mapped to our second web server for another application. I'd like to use one of the addresses from the block to setup the second web server but am unsure as to how to do this in the Netopia R910's menu. I had it to the point where I could ping a second public ip address from the internet, but couldn't get past that.