Start external SWF when movie clip gets to Y position

I have one movie clip that when clicked on moves to the left of the screen, after it gets there I want another and exteral swf to load. But I dont know how to get the external clip to load after the movie clip gets to the left side of the screen…
Here is what I got so far…

square_mc.onRelease = function()
{ square_mc._x = 30;
square_mc._y = 180;
square_mc.onEnterFrame = function()
if(square_mc._y = 180)
{ _parent.createEmptyMovieClip(“container_mc”, _parent.getNextHighestDepth());

Baicly the idea is when square_mc get to the Y position of 180, run the external clip.

Any ideas, thank you.