If the challenge is to deliver on a server farm you can setup a logical server, it's not the most advanced but will allow you to add more than one server to receive the at the same destination port/service.
If it's just trying to map several services on a single public IP and deliverer it to it's own different IP, on a per service bases, then I think it might be like Dameon says. I do have a question though.
If the "world" is going for a high-port on the gw IP, why are you forcing the redirect to a standard port like http? Why don't you put the listening http at the same port you published to outside world?, by simply assuming you MUST redirect destination port you are narrowing down your options by your self:
The above screenshot might has well be a group of high ports or what ever you need, just make the services on the server side match the original destination service and you are on with a bundle of ports in a single NAT rule.
Hope this helps
Carlos Santos