How do I make a blank button with a transparent hit area with AS?

Hi all - pardon my first post.
I’m trying to make a button symbol with a transparent hit area - surounded but a dynamically drawn border. Heres what I have.
I have a simple AS script that uses goTo and lineTo (plus a randomizer to make sure the buttons are skewed and differnt everytime) to create a “sketchy box” as my button. My script resides in a movie clip withing the “over” state of a button symbol. Now the active hit area is ONLY the line elements. Question : How in the world, using only actionscript an I make a second, transparent area inside of the sketchy lines to make the whole button symble clickable?? Thanks!!