Reversing Scroll Direction

programming flash
1

I have a website I am working on which requires two objects scrolling across the screen. I have done this fine. But I recently learned they need to be scrolling in different directions. How do I do this?

onClipEvent (load)
{
   xcenter=150;
   speed=1/10;
}
onClipEvent (enterFrame)
{
   _x-=(7);
   if (_x > 0) _x=-792;
   if (_x < -792) _x=0;
}