Circular mask w/ feather

Hey all,

I was wondering what the best way to do this is:

I’d like to have a circular mask that as the user drags their mouse around, they see what’s in the circle. Not too hard. But what I’d like is a very soft edge on that circle. What’s this gradient tool all about in Flash? Is that something I can use to do maybe a radial gradient (foreground to transparent) on a circle shape?