Well there might be an easier way, but on a lark i tried renaming the Applications folder to see what would happen, and the button then jumped to another directory, i can't remember which off hand.
i played around with creating aliases and symbolic links and i managed to get the button to point to the directory i wanted. i dont remember which it was that worked (link or alias).
i did it originally because under 9 i had my apps all on one drive, so i was trying to get it pointed to that drive. but in the end i decided i liked it better the way osx had it by default, so i just move the original Applications directory back.
note there is some weirdness hwen you do this though. you have to log out and back in sometimes to give it a chance to clear its head i guess.
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raia