Mask Move with mouse

programming flash
1

i have a problem in moving the mask with mouse
someone tel me

what is the right code

here is the code i use

// myImage is bakground image
// myMask is masking
stop();
myImage.setMask(myMask);
onEnterFrame= function(myMask) {
_root._xmouse - this._x ;
_root._ymouse - this._y ;
_x += myMask ;
_y += myMask ;
}

//myMask.onPress = function() {
//startDrag(this);
//}
//myMask.onRelease = function() {
//stopDrag();
//}