Hit test and sounds - help please

1

i am working on a little game in flash8 and action script.

Objects fly around and land in areas randomly. When they land in an area they dont move until the mouse has touched them. The problem I have is I want to play sounds when they land in the areas, but my hittest is constantly running so the sound keeps starting to play, I only want to play the sound through once.

if (_root.ball_mc, hitTest(_root.zone)) {

         _root.sndChannel02.start(0,1);
}

any help massively appreciated !

thanks