Simple question

I am working on a simple scroller rite now. What it is suposd to do is scroll a row of buttons to the left when you go over the left button and to the rite when you go over the rite button. i am pretty sure i have the wright syntax but i alwasy get an error.

this.btn1.onRollover = Function(){
onEnterFrame;
this.scrolller._x +=3;
};

and its the oppisite for the other button, i have a feeling its something stupid, but if anyone knows how i can fix this please let me know.

Thanks,
kool