How do I convert any video-files to audio-files using Applescript?

Hi, when you are in finder you can right-click on a video to choose the option encode. From there you can choose an option: only audio. I want to use this in applescripting to automate things but I searched for three months now and I can't seem to find out how. I searched the web, the applescript dictionary,... but without results.

I would be very happy if anyone can tell me how. Wether you can give me a link or you can directly say how, then please do so.

thanks in advance,

Kanti Kuijk