Alpha channel and mouse events

1

I have some png images which were converted to movieclips and exported. I would like all clicks on the transparent parts of the png to be ignored by a movie clip on a closer layer and have a movie clip under the transparent parts receive the event. Is there a way to do this? When I convert the symbol to a movie clip, the authoring tool automatically puts a bounding box on it so all clicks in the bounding box are detected. I tried searching mouse events and alpha channel stuff on the forum. Maybe I missed it. Anyone have ideas?