AppleScript for opening different iTunes libraries

Question

I want an application that will, at the press of a button open one of my two iTunes libraries, as I have to switch between them with frequency. Unfortunatly, I can't figure out how to tell iTunes to open a specific library. I have what I tried pasted below. No mater which button I press, (except for "cancel" of course!) it just opens the last used library. What am I supposed to do?
Thanks.
tell application "iTunes" to quit
display dialog "Choose an iTunes Library to open" buttons {"Normal iTunes library", "mp3 library", "cancel"} default button 1
copy the result as list to {buttonpressed}
if the buttonpressed is "Normal iTunes library" then
tell application "Finder" to open POSIX file "/Users/benlevy/music/iTunes/iTunes Library"
end if
if the buttonpressed is "mp3 library" then
tell application "Finder" to open POSIX file "/Users/benlevy/music/mp3 iTunes library/iTunes Library"
end if
if the buttonpressed is "cancel" then cancel
end

Answer 1

I know those things! I do switch manually all the time. I want this program to eliminate the hassle.
The reason for having two libraries is because I have an mp3 player that uses the iTunes library file structure to copy music (including the artists, albums, genres, etc) onto its hard disk. Unfortunately, it is small (2Gb) and it only handles mp3s. Luckily, I have been able to create a work flow that saves all the high quality aac files from my regular itunes library, and copies highly compressed mp3 versions of them to my "mp3 itunes library." I need to open the mp3 library to sync my mp3 player, but to listen to music I use the normal library. I don't want to deal with two copies of each song in 1 library!