Help with this effect

Im curently taking up flash as a course. just started so im kinda new to the whole scripting thing. ive asked people how to do this http://www.bio-bak.nl/ and they say its very easy but no 1 has told me how it could be done. if any 1 has a video tutorial or has the .fla pls i would be forever greatfull if you were to give it to me.