"Moving grass" at the bottom of the page

Hello everybody! I got this cool effect in my mind I’ve seen around. Its like having two or more rows of “grass” at the bottom of the page and have them move at a different speed from left to right. It creates this releative feeling and brings the site alive.

I understand to achive this you have to duplicate a movieclip untill it covers the page width + some more and then tell it to move form one side to another.(using laco tween for example.) I don’t need it to be continious, just have it move a little bit when user clicks on a new secion of the page. I’m horrible with AS though. Has anybody done this before or know any resources I could check out on this subject? Thank you alot!

http://www.kirupa.com/developer/mx/grass.htm