Controlling sound in a different _level

I have a loaded SWF file in _level1 that has audio in the timeline. I am trying to control the volume of this loaded SWF with a ‘mute’ button in the main SWF file. On the first frame I’m using the code:
my_sound = new Sound(_level1);
and then on the button script I have:
mute_btn.onPress = function(){
my_sound.setVolue(0);//mute volume

but it’s not working. Am I missing something? Is the new Sound(_level1) not valid?