multiple DMZ?

i am playing socom ii on the ps2 online though my router, i have it set as the dmz host and it works. My friend wanted to come over and plug into the router to also play, but he cant get on cause i cant set up multiple dmz host, i think my ip is ....103 his is ....121

The only thing I can think of, is to find out which ports the game uses and forward those through the router.