Communicating with external swf

This is my question, how can I communicate with an external swf, thats loaded into an empty movieclip?
I would like to know if Im heading the right direction.

On the root timeline I put this script.

this.createEmptyMovieClip(“box”, 1);

And then when I click on a button I want the external swf, which is test.swf to gotoAndPlay at keyframe.

On the button

on (release) {

But somehow its not working.
Help please.

Thanks in advance.