Create List of Objects as3

I have three circles: a red, a blue, and a green. Each one is draggable. There is a yellow box, this is the canvas per se. And a “DONE” button. What I’m trying to do is when the “DONE” button is clicked a list is complied of all the circles’ instance names on the yellow box. So i.e the blue and red circle have been dragged on to the yellow box; I click “DONE” and a list is compiled: (blue, red). I though this would be simple but it doesn’t seem so straight forward… any push in the right direction will be appreciated!

Thanks