ActionScript 3 呼叫元件庫中的MovieClip

/*
原件庫中有一個img_box的影片
在原件庫對該影片點右鍵->屬性 匯出給ActionScript使用及匯出至第一影格都要勾選
就能呼叫該元件出來
bg.9sweb.com / by egg
*/
for(var i=1;i<=5;i++)
{
 this['mybox'+i]   = new img_box();
 this['mybox'+i].y = 55*i;
 this['mybox'+i].addEventListener(MouseEvent.MOUSE_DOWN,fn_startdrag);
 this['mybox'+i].addEventListener(MouseEvent.MOUSE_UP  ,fn_stopdrag);
 addChild(this['mybox'+i]);
}

function fn_startdrag(event:MouseEvent)
{
 //event.target 搞好久才知道要用這個XD
 event.target.alpha = 0.8;
 event.target.startDrag();
}

function fn_stopdrag(event:MouseEvent)
{
 event.target.alpha = 1;
 event.target.stopDrag();
}