Checking an external HD for iTunes files

Hi there.
I'm a new user & searched the forums, but couldn't find an easy way to do this...I've done a few different ways, but none are completely successful...yet
I keep all my music & iTunes stuff on an external HD.
I intend to have Hazel on 2 computers in the house checking the external HD music folder.
If I d/l a song off of iTunes, it's on that HD, & I want Hazel on the computer that DIDN'T download the song, to see that something new has been added to the subfolders & add it to a playlist in iTunes.
If someone has a foolproof way for this to work, I'd love to hear it!
Sometimes I've almost got it working, but it seems to not go into the requested playlist for some reason.
I'm a new user & searched the forums, but couldn't find an easy way to do this...I've done a few different ways, but none are completely successful...yet
I keep all my music & iTunes stuff on an external HD.
I intend to have Hazel on 2 computers in the house checking the external HD music folder.
If I d/l a song off of iTunes, it's on that HD, & I want Hazel on the computer that DIDN'T download the song, to see that something new has been added to the subfolders & add it to a playlist in iTunes.
If someone has a foolproof way for this to work, I'd love to hear it!
Sometimes I've almost got it working, but it seems to not go into the requested playlist for some reason.