Well this is a toughy. Since we cannot define our IP rules with that kind of precession on the RV042 we really can't do that. Now here is a screenshot of something that may work. I say "MAY" as in a real big maybe! The thing is, we can't create a rule that says "send this LAN to this WAN"; otherwise, you probably would not even be asking.
I think if we deny traffic from the WAN to your IPs they should respond back to that particular interface, but there is a small catch. Since our two options on the RV042 is either "Smart Link" or "Load Balance" we are stuck in a little pickle. This is because the client (LAN) is usually the one to initiate the connection and the router will Load Balance and IT will decide which WAN port to go out on. So, my little idea may not work. I am not at work at the momment so I cant take a look at a RV, but I do beleive with the latest firwares we can do protocol bindings and from there we can split traffic.
Anyway, what we need to battle with is "Load Balancing" and we need to place rules that will work in this mode. Let me know if this helps, or maybe someone else will step in with a better idea.
