How can I make a sliding volume control?

I’m looking for tutorial on this one, but I haven’t had any luck yet. Luckily I remember the Kirupa message board where I’ve always received great advice!

I would like to make a volume control bar like on the website: You can see the volume control at the bottom of the screen. I like how you can press your mouse key to drag the volume down and back up again. How did they do this? Would I need action script for this? Any tutorials available on this sort of thing?