Range Error.How can make the movieclip always on the top

I want to make the bar on the top at all time but it seems not work when I addChild.  When I add container. it occurs an error.

RangeError: Error #2006: The supplied index is out of bounds.

          at flash.display::DisplayObjectContainer/setChildIndex()

var container:MovieClip=new MovieClip();

addChild(container);

var menubar:MovieClip=new Menubar();

menubar.x=0;

menubar.y=859;

menubar.name="menubar";

container.setChildIndex(menubar,(numChildren-1));

addChild(menubar);

menubar.recipe_btn.addEventListener(MouseEvent.CLICK, onRecipeClick);

function onRecipeClick(evt:MouseEvent):void{

addChildAt(recipe,1);

}

recipe.foodIcon.addEventListener(MouseEvent.CLICK, onFoodIconClick);

function onFoodIconClick(evt:MouseEvent):void{

          removeChild(recipe);

    addChildAt(recipeFood,2);

}

menubar.product_btn.addEventListener(MouseEvent.CLICK, onProductClick);

function onProductClick(evt:MouseEvent):void{

addChildAt(product,3);

}

menubar.cupon_btn.addEventListener(MouseEvent.CLICK, onCuponClick);

function onCuponClick(evt:MouseEvent):void{

          addChildAt(cupon,3);

}

menubar.location_btn.addEventListener(MouseEvent.CLICK, onLocationClick);

function onLocationClick (evt:MouseEvent): void{

          addChildAt(location,3);

}