Best method for zoned sound?

I am trying to get sounds working in my game and would like to have different sounds play and loop depending on where my is within its parent mc (

So if my is 1000 pixels wide and is <= 500 it will play and loop sound1, and if is > 500 it will play and loop sound2.

I have the playing and looping done with a SOUND_COMPLETE listener but if one sound is playing and moves from one “zone” into the other I cant get the sound to stop and the new one to start. Currently it will only play the new sound once the previous sound ends.

I have probably gone about it all wrong and there will be a much simpler way to achieve this but I cant work it out. What is the best way to do this?