Stop BG sound when i load a LoadMovieNum file

I planned a website using many levels of "loadmovienum"s, loading external flash files.
On the main swf file, that will load the external files, theres a “simple” sound button (movie clip), for turn off and turn on, the background sound loop. So, the sound is being played since the user click above the button (mc) to stop it. At same time, the same sound button (mc) controls an animation (mc) nested in it. So clicking the sound button, you stop the sound and the animation at same time, or restart both.

In one of the external files to be loaded, theres a mp3 player mc. Would be interesting that when you load this external file, the background sound and the animation (nested into the sound button mc on the main swf file) could stop, to dont make both sounds confusing the user.

So my challenge is: how can i turn off the sound button inside the main swf file, when you load the external file holding the mp3 player?

Thx in advance.