Your follow up posts suggests that there is considerably more to your situation than you asked about in your first post. In your original post, you wanted all (local) traffic to go out via the wired interface and "all other" traffic, which would mean things that are not a local or defined static route, out your wireless. You updated situations sounds A LOT more like a VPN scenario.
In this case you can either add static routes, stipulating exactly how to get information to 'Server A', or you can change your approach to use NAT, or more specifically, IP Masquerading, between the two domains (or hosts). If you are running Linux this is relatively easy and can be done with Iptables. I don't know if there is an equivalent tool under Windows, but maybe something like winproxy or wingate, based on a quick search.