Change loaded movie from child

Question

Hi,
I am new to AS3. Here I want to ask how to change the loaded movie from child?
Here is my working code, but it doesn't works...
Root:
var contentMovie:MovieClip = new mcMain;
contentMovie.name="content_mc";
addChild(contentMovie);
Child Content:
changecontent_btn.addEventListener(MouseEvent.CLICK,LoadContent);
function LoadContent(event:MouseEvent):void
   parent.contentMovie = mcNew;
When I try to run, Flash shows the error "1119: Access of possibly undefined property contentMovie through a reference with static type flash.display:DisplayObjectContainer."

Answer 1

use:
var contentMovie:MovieClip = new mcMain();
contentMovie.name="content_mc";
addChild(contentMovie);
Child Content:
changecontent_btn.addEventListener(MouseEvent.CLICK,LoadContent);
function LoadContent(event:MouseEvent):void
// the next line doesn't make any sense but if it did, this is how it should be written
  MovieClip(parent).contentMovie = mcNew;