Call a function when "Play Now" is called?

[Jugdish]

I'm working on a script and I'd like to have one of the functions get called anytime the Now Playing playlist gets auto-populated with tracks when a track is double-clicked from the library. In the prefs, this is referred to as the "Play Now" command, so I guess what I'm after is a way to hook "Play Now" so that my function gets called when it gets called. Is there any way to do this (or something that would have the same effect)?