This script will apply user-entered text to the "Category" tag of each of the selected tracks. iTunes 5 or better.
(Note: In order to launch this PowerPC-era script on an Intel machine, it must first be opened and then saved using AppleScript Editor, which is located in your /Applications/Utilities/ folder. More information is here.)
Convert Roman numerals in selected tracks' name to upper case
Capitalize the first letter of each word in selected track names
Correct song titles listed as "Artist - Song Name"
Append user-entered text to beginning or ending of selected tag of each selected track
Set the Plays of selected tracks.
Sort purchased tracks into discrete playlists by name or account ID