I'm guessing its one of the huawei 3G modems, that is USB into the back of your laptop. My guess is if you want to turn this wireless, then you might need something like a 3G/Wifi router, like a draytek etc. Never used one myself, but as I understand it, the draytek is the only one that will take the USB modem itself, unlike the linksys ones which require a 3g datacard.
Your other option though, would be to use ICS on your pc which has the USB modem plugged into it. THis means wiring cat5 from your xbox to your pc/laptop, but might be worht a try. I would do it anyway as a test, seeing as it wont cost you anything and would prove that your 3G is good enough for gaming before splasning out for hardware.
Wexfordman