I'm failing to add 2 dynamic created movie clips "sb and contents" to dynamic created movie clip "scrollbox" any assistance would be greatly apreciated thanks sincerly sybershot

var scrollbox:MovieClip = new MovieClip();
this.scrollbox.x = 50;
this.scrollbox.y =50;
this.scrollbox.width = 340;
this.scrollbox.height =520;
this.scrollbox.addChild(sb);
this.scrollbox.addChild(contents);
this.addChild(scrollbox);