OnMouseMove ONLY onRollOver

Hi there, I have a simple enough Q… I am trying to ignite an onMouseMove function with an onEnterFrame event ONLY when I rollOver a certain hotspot…
Ok,Starting with:…

My_mc.onRollOver = function(){
var mouse:Object = new Object();
    Mouse.addListener(mouse);

    onMouseMove.mouse = onEnterFrame = function () { 
trace("OK");}
}

The trace fires on the rollOver… But when the mouse STOPS, Trace IS still Firing.
Also I want to Kill the function, when I rollOut! … >
It should be nice and simple, but im having a few problems with general syntax of AS.

Could anyone give me a hand!?? Thanks:ch: