Pan image, randomize

Hi!

I´m looking for an effect that pan your image randomized over the image. Right/left/up/down without any mouseclick because it is for a screensaver.

My code right now just move to the right. I want it to move in all directions.



onClipEvent (enterFrame) {
//this moves our clip 5 pixels to the right every frame
this._x-=5;


I have found this as well but it also just go to one directions:
http://livedocs.adobe.com/flash/9.0/main/wwhelp/wwhimpl/common/html/wwhelp.htm?context=LiveDocs_Parts&file=00000958.html

Does anyone know any tutorial or the code for do this effect?