SuSEfirewall2 DMZ

Hi there, I hope that this question wasn’t discussed before. I have a little problem with my SuSEfirewall on SuSE 9.0. I’m using two different internet connections with fixed ips, one masqueraded DMZ and a masqueraded internal network. I’m forwarding two different ips to one client in the DMZ. It depends on the routing table (default gateway) for which ip I get a response. When I change the default gateway I get response from the other ip. Is there a possibility to route the packages to the Interface where they are from? Thanks a lot joerg