Problem with for action

ive got a problem with my actionscript with a scroller bar. i want ot do it differently to the kirupa tutorial but im stuck on getting the actionscript to work. ive got

on (press) {
this.startDrag(true, 140, 200, 435, 200);
}
on (release) {
this.stopDrag();
}
onClipEvent (enterFrame) {
for (_root.slider._x=_x+1) {
_root.num = _root.num+1;
}
}

i cant get the last bit to work so could someone help me plz to try and get the num to go up every time the sliders _x axis goes up
it would be a great help
thx