If you are on OS X you could get around it writing a small script and folder actions, I’m sure there is an equivalent for this on PC. Some id taggers pick up info from the filename (i use kid3) with the press of a button and allow you to perform this action on multiple files at once.
There’s always id3tool lib/command line utility but even me as a programmer just fire up iTunes to change id3 tags unless it’s a specific tag not accessible from iTunes.