1 roundtrip to Europe plus 1 transcon should about do it. I have no idea whether you can find good enough fares to make it worthwhile or not. Charlotte is probably a tough town to initiate a long and cheap US Airways mileage run from...

The US Airways board will have lots of information. I don't know whether US Airways would comp your Silver through all of 2003, or if they offer a fast-track/challenge for early 2003. (They gave me Gold in 1998 for flying 10,000 miles in two months, part of a targeted promotion.) I also don't know if another airline would comp you a low-elite status based on your US Airways status. However, I'd explore all of these options before booking a mileage run. If you end up wanting to do the run, you probably need to be in the air tomorrow or Saturday morning at the latest.