Replace Genre with "AA %_folderpath%"?

Am I @%#$ing up the placeholder? Am I putting the script in the right place?(actions) Is it simply not possible?

See, I am going on a 3 day road trip, and I've got a LOT of music (~200gb). I don't want to have to be too distracted on the road searching through my entire collection(5g iPod with 250gb hdd), and I mainly only want to listen to the new stuff I just got for the trip (about 3,000 songs). I got the tunes arranged in folders, and sub folders, with a lot of different artists and albums, so I'd like to ultimately be able to browse the folders via my Genres.

I know the easiest solution may be to install Rockbox(which I have, as a matter of fact), but let's face it; RockBox is a bit of a battery hog.

Bottom-Line: Replace "*" Genre with "AA %path%"
Any ideas guys?

Use Format value instead of Replace:

Action type: Format value
Field: GENRE
Format string: AA %_folderpath%