Generally, the answer to this question seems to be NO. Wireless Access Points are designed to allow computers to share a connection to the internet via a modem immediately attached to the WAP, not act as bridges.
I have sort of the same situation as you, and did a bunch of Googling on it a little while back. Situation: we had to move the modem and router to my roommate's bedroom, so now I have to go wireless (it was in my room before, so I was just connected right to it at 100mb with ethernet cables.) One of my computers is USB 1.1 (with a wireless B adapter) which means it's DAMN SLOW over the network using my wireless adapter. Now, I happen to have an extra access point laying around, and I did not want to go out and buy either a wireless networking PCI card, or a USB 2.0 expansion card and a wireless G adapter -- instead I wanted to just hook MY two computers up to the extra WAP, and have it in turn act as a wireless G bridge to the primary one. As I previously noted, the answer I seemed to mostly come across was a negative. However, I don't know if something like this might address our situations -->
http://forums.anandtech.com/messagev...VIEWTMP=Linear
It would make sense that you could use these things as basically a bridging switch if you wanted to. Of course, obviously the networking companies have a vested interest in that NOT happening so as to avoid conflicting product usages (why pay $50 for a lousy USB network adapter for one PC, when you could just get a WAP that gives you four ports to plug into.)
It may complicate things having to deal with a second firewall in the mix, but I guess that's the price you pay for trying to circumvent the product's intended use.
I might just try this myself.