sound on/off in video

hi!
i want to create an on/off button for the sound of a video.
OFF is simple to do with:

on (release) {
stopAllSounds();
}

but i have difficulties with the ON, as i can not address the sound directly (f.e._root.sound1.setvolume or whatever) because the sound is integrated in the video.
but i guess the answer is quite simple is i have seen it quite often in other peoples videos.

hope to get an answer.

thanks a lot
anna