Problem in Drawing a square/rectange

1

Hai!!
I have created a MovieClip using CreateMovieClip to draw a square or Rectangle. The problem is when mouse Moved it , it is creating many number of squares below it.

Here is the code which i ve tried…

var sx:Number;
var sy:Number;
var swid:Number;
var :Number;
var mouseListener:Object = new Object();
mouseListener.onMouseDown = function () {
this.isDrawing = true;
sx = Number(_xmouse);
sy = Number(_ymouse);
};
mouseListener.onMouseMove = function () {;
if (this.isDrawing) {;
swid = Number(_xmouse-sx);
**** = Number(_ymouse-sy);
};
updateAfterEvent();
createbox();
};
function createbox() {
this.createEmptyMovieClip(“square_mc”,this.getNextHighestDepth());
square_mc.beginFill(0x0099FF,100);
square_mc.lineStyle(0,0x0099FF,100);
square_mc.moveTo(sx,sy);
square_mc.lineTo(sx+swid,sy);
square_mc.lineTo(sx+swid,sy+);
square_mc.lineTo(sx,sy+****);
square_mc._alpha = 50;
square_mc.endFill();
updateAfterEvent();
}
mouseListener.onMouseUp = function () {
this.isDrawing = flase;

};
Mouse.addListener(mouseListener);