setMask(); problem? Am i doing this right?

1

Ok, here’s my code:

for (i=0; i<200; i++) {
    circle.duplicateMovieClip("circle"+i, this.getNextHighestDepth());
    randX = Math.floor(random(Stage.width));
    randY = Math.floor(random(Stage.height));
this.banner.setMask(this["circle"+i]);
    this["circle"+i]._x = randX;
    this["circle"+i]._y = randY;
}

circle is a movieclip that has a circle starting at 2px by 2px and expands to 100 by 100. Banner is just a movieclip, but I would like these expanding circles to act as a mask to reveal the banner. This should work, but isnt, I know im overlooking something, but can’t figure it out!