Layered transparent images

I’m still really new to Flash & actionscript, so bear with me. I’m making a “dress-up doll”, I guess you could call it. And the clothes that you put on the doll are transparent images, and each type of clothing/items are set on their own layer (i.e. hair, tops, pants, etc). The problem that I’m running into is that currently each image is clickable based on the actual size of the image (i.e. including what is transparent), rather than what is just viewable. Hope that makes sense.

So for example, if the doll is wearing a tube top, you can click all around the tube top to select it, not just the tube top itself. While I can crop the images to be tighter, this is going to cause some issues in the long run, as the doll gets more layered with items that are on top of each other – the user will think they’re selecting one item, and actually be selecting something else. I want each item to be selectable based on its transparency, not on the overall image itself. Am I making sense? While I can redesign the whole thing to make the items on the doll itself not clickable, I’d really like to keep that functionality – it’s how the user changes colors, etc.

Can you point me in the right direction? What do I need to start looking at to make this work?