Default video sound is mute. But when i also can turn on from the volume bar.

I use FLVPlayback from CS 4 to input videos.

I need default sound is mute, but I can turn it on  when I need it from volume bar.

Please see my attachement:

Here is the AS:

stop();

button1.addEventListener(MouseEvent.CLICK,clickListener1);
function clickListener1(event:MouseEvent):void {
    gotoAndStop("30sec");
}

button2.addEventListener(MouseEvent.CLICK,clickListener2);
function clickListener2(event:MouseEvent):void {
    gotoAndStop("30sec2");
}