Last spring I made a booking on the USAir website for a non-refundable ticket. My plans fell apart, but I cancelled the flight before the day and thus got a credit to apply -- with, of course, a $100 change fee -- to future travel, within one year from the original purchase date. OK, fair enough. Now I'm looking to use that 'credit'. The US website lets me 'modify' the earlier, cancelled, reservation. Again, OK. BUT ... my question is .. do I have to go directly through US (either online, on the phone or in person) to apply the 'credit' to my next booking, or is there some way to enter it in Expedia or _any_ of the other online booking services? If so, how? Thanks.