YOU REGISTERED ON A REVERSE ENGINEERING FORUM TO ASK A QUESTION ABOUT INFRASTRUCTURE DESIGN.
Reverse engineering: we take some code, or a device, or a DVD menu system if you're particularly geeky (cough

), fiddle with its bits, and make it do something different.
Infrastructure design: not the same thing.
Why would you go through the trouble of registering here, a completely inappropriate forum for your question, when it would take you just as much effort and time to register somewhere else that may be more appropriate? I could understand it if you'd been posting here for years and just had an off-hand question for the community of people you already know (as many of us do). But you're a brand new user! You made your account specifically!
To be frank, I don't even understand your problem. I can't tell if you're trying to do this with ISA server (as you complain in your second post you couldn't get it working) or with Squid, or with some other hip and happening solution.
And now I've wasted even more valuable table space (and eventually CHM space) complaining about you. Sorry, everyone.