Connecting to XBL via a laptop gateway?

I’m pretty sure there’s a way to do this but I can’t figure out exactly what I need to do. I’m trying to use my laptop as a gateway to connect my XBox to the internet for XBL. The thing is, I’m connected using one of those cell phone wireless 3G cards, not really sure if that would have anything to do with how I would make it a gateway or not. Any help would be greatly appreciated :]

here ya go