Analog signal through Arduino - mute circuit

I need to build a mute circuit for my amplifier. To do this I need to send analog signal into Arduino and exit through output pin.
Is it possible to do this?
If possible can someone please help me with some codes or reference to study?

Pgamage:
To do this I need to send analog signal into Arduino and exit through output pin.

No, you don't, that would be a terrible idea, it would destroy the sound quality.
Keep the signal analog.

This might be useful: http://sound.whsites.net/articles/muting.html

Pieter

I think digI pot is the next option for me. However the sound I am interested is just the sound of blow to the microphone.

Use the arduinio to run a relay or transistor for your audio line. The audio can't run direct through arduino, it is largely a digital I/O device and just doesn't work this way.