Could you be a bit more specific on what you are trying to do? I'm assuming since you are using VS2005/C and you posted this on the iControl forum that you are using the iControl API and this is an iControl question.
If you are writing an iControl client application, which method are you calling to get this information?
I could understand if you are doing log gathering on your backend server (Pool Member) and you are retrieving the BIG-IP's address instead of the true client address? If this is what you are running into, you might want to turn on X-Forwarded-For in your virtual server config. It will forward the client's true address in the X-Forwared-For HTTP request header.
Again, I'm not sure if this is where you issue lies, so if you could clarify a bit exactly what your application is doing and whether this is an iControl vs. a system configuration question, that would help us.
-Joe