Buttons move into place - but what script

This is certainly a question for the scripters here at kirupa -

On the following site: http://www.subvitamine.com

if you go to say the services page you will see four buttons appear, communications, interactive etc. now if you click on the interactive button for example, the other buttons move into place and of course this applies to all the other buttons. Great effect and i’d always wondered how it is done. I can see that the movement on the site is done with easing actionscript and I can manage that ok, but getting the buttons to move around like that is great. Anyone have a sample fla or a tutorial to point me at would be great.

Thank you.