Random growing circle mask revealing an image

From this tutorial:

http://tutorials.flashmymind.com/2009/02/random-mask-circles-on-image/

Pretty neat effect, I wanted to use this for a gallery transition, but I have a problem.

Does anybody have an idea how to know when image has been completely revealed so I can stop the enter frame listener and remove this growing masks, otherwise this is pretty useless :smiley: