So I've figured out how to do it if anybody cares. Make a symbolic link of the itunes library file. ( I don't think just an alias will work from what i have read about it). I used a program called
SymbolicLink to make the link. first overwrote the tower library file iwth the one from the PB. With the tower drive mounted on my PB I made a the link from inside the towers itunes folder. Then copied that link to my PB's itunes folder, deleted the original library file on the PB and renamed the link to be "iTunes 4 Music library".
Now when I make a change of rating, playlist or whatever both computers technically use the same library file. The Itunes Music location in itunes prefs on both computers point to the same directory on the tower which has all my music.
what did this accomplish My ipod on the tower gets updated with smart playlist and rating that i changed on the PB. And 1 less wire to fiddle with every day when I take my PB to work.
you do however have to still authorize the second computer to play music bought from iTMS on the first which is no big deal.