Movement and Loop with AS

programming flash
1

I´m using this AS to movement a MC

[AS]onClipEvent(enterFrame){
this._x += -1;
}[/AS]

but not looping, how can i loop with AS?
i try to do this with infinit fake background, just one piece of image and loop, but i just got this with timeline animation… how can i do this with AS?

thanks!