iPod Change artwork when changing album name

[doobs]

I have lots of songs that are from the "Best of " albums from several artists. I prefer to have songs listed in the album in which they first appeared and so I have changed the album for most of these songs from the "Best of " album to the appropriate original album. Now, the problem is that the artwork is still that of the "Best of " album. I have tried clearing the artwork and re-getting it using the facilities built-in to iTunes (8.2.1), but it just re-downloads the same "Best of " artwork. I really do not want to have to manually get the artwork for each of these. Does anyone know how to get iTunes to pull the artwork for the album that I have written in the appropriate song info "Album" field? Thanks in advance...