Getting filename of externally loaded swf

Hi, all, I am trying to figure out how to get the actual filename of an external .swf when loaded into another movie clip.

var toTrace:String = getChildAt(0).name;
trace(toTrace);

That is what I have. It gives me the instance name, which does me no good, because it is a relative instance name. My situation is that I have a few buttons, when clicked they load external .swf into the stage at index 0. I need to know how to reference the currently loaded external file.

-ae