Need Help Making a Volume Meter

Is there any way to get the amplitud data of a sound? What i am trying to do is make a volume meter. I want the height of a mask to be controlled by the amplitude of a sound. That way to graphic underneath the mask will constantly change, like a volume (peak) meter. Is there a way to do this? I hope this describes well enough what i am trying to do. Any help is appreciated.

http://www.kirupaforum.com/forums/showthread.php?s=&threadid=27723