RemoveChild from stage with button?Problem.help

Im new in AS3 and im having trouble in this one.

Ill explain with the following code which is on the first frame of the stage

***import flash.display.MovieClip;

var line:Line=new Line ();
addChild(line);*
**

Line is a movieclip with a picture in it, which loads dynamicaly with the following code inside the movieclip “Line”

var line:Loader = new Loader();
var fileRequest2:URLRequest=new URLRequest(“line.png”);
line.load(fileRequest2);
this.addChild(line);


The second movieclip is a button (mybutton) which i want to put on the stage and on click to remove the “line” instance from the stage.i putted inside the button the following code with no succes

this.addEventListener(MouseEvent.CLICK,_click);
function _click (event:MouseEvent):void{
this.parent.removeChild(line); }


i get the following error:1120: Access of undefined property line.
Plz Help Ive wasted a lot of hours without result!!!