Help: clip won't fade out!

programming flash
1

I want my movie clip (a simple box) to fade out when the mouse isn’t near it. I put together this code myself and it doesn’t work. Keep in mind that I know near nothing about actionscript.

 
onClipEvent (mouseMove) {
 xclip = getProperty(_target,_x);
 yclip = getProperty(_target,_y);
 xcurs = _root._xmouse;
 ycurs = _root._ymouse;
 alphax = Math.abs(xclip-xcur);
 alphay = Math.abs(yclip-ycur);
 if (alphax<200) {
  if (alphay<200) {
   talphax = Math.round((200-alphax)/4);
   talphay = Math.round((200-alphay)/4);
   allalpha = talphax + talphay;
}
}
 setProperty ( _target, _alpha, allalpha);
}