Can you *force* BM to use one NIC for proxy requests(client connections), and the other NIC for proxy filling?

What I would like to do, is keep my BM server from being connected directly to the internet (policy states that devices must connect through out Cisco PIX). But, I want to setup with two NICs for performance reasons, and auditing reasons.

It appears that the Public/Private settings have no effect on this.... at least when they are on the same subnet.