Stopping Timeline's sound but continue the video's sound

Hi folks!

I need help to solve this problem. I can’t seem to get it work out.

I have a music playing in Timeline (looping forever) when the flash site starts.
In some sections of the flash site, there is a video section where users can watch a video.

When the video is played, I would like to stop the sound in Timeline so it doesn’t interfere with video’s sound.

For loading the video, I am using Video Object, the code is simply:

var my_conn:NetConnection = new NetConnection();
var my_stream:NetStream = new NetStream(my_conn);

Many many thanks in advanced for your help!!

ps: I have tried following links, but no luck to me.