So here is my situation.  I came into this job with this all set up.  The network is set up to use 1 external ip xx.xxx.xx.226 via NAT.  I have added a web server and because it is using 1 external IP it is causing conflicts with the user using the same external IP.  So I am getting a collision. 
What i need to do is have the web server use its own external IP. xx.xxx.xx.228  but I am unsure how to do make it use that because it is in our internal LAN. 
Any help would be greatly appreciated.