Arduino Ethernet Networking Setup Help

This is part Arduino and part not Arduino, but I was wondering if someone else has gone through this or knows a solution. I have an Arduino with Ethernet Shield hooked up by an RJ45 cable to my MacBook Pro that has sharing internet through ethernet enabled. My MacBook is connected to the internet with WI-FI of course, but through an Airport Extreme hooked up to a router. My question is, how should I go about forwarding port 80 for my Arduino? To simplify, Arduino--->MacBook--->Router--->Airport Extreme. I know my Arduino's private IP and my MacBook's private IP, but Airport Utility asks for an IP that begins with 10.0.1.X. Someone clear my confusion.

You can’t… you first need a cross over cable, then some kind of internet sharing (eg ics)

cjdelphi: You can't... you first need a cross over cable, then some kind of internet sharing (eg ics)

I think ICS may be windows.