Mute button in Actionscript

I did the mute button. Declared the muteBut as Movieclip and I have another
Movieclip called SoundOnBut.

What it does is when user clicks on the muteBut (which is initially started up
on the screen) the sound will be mute. This one I can achieve. But I need to
know how can I swap the muteBut into SoundOnBut when the user clicks on the muteBut to mute the sound.

I also want to do it via versa, when it is being muted, user clicks on the
SoundOnBut to unmute the sound and swap the symbol back to the muteBut.

How can I achieve this?