Controlling volume in Flash Slide Presentation


I am working in Flash Slide Presentation mode. I have a started a sound file playing on the “master” slide and I want it to play throughout my entire presentation. However, on a couple of slides, I want to play some short voice clips. How can I “turn down the volume” a bit on the main sound file so as to hear the short voice clips? And then turn it back up when the voice clip ends?

I understand basic Actionscript. Can anyone tell me the code or point me to a tutorial which I can use to accomplish this?

Thanks in advance.