If you need to put something inside a Container and have it always visible, even when the content gets scrolled, you can add it to the rawChildren of the Container.
var container:Container = new Container();
container.width = 100;
container.height = 100;
var label:Label = new Label();
label.width = 200;
label.height = 20;
label.text = "I'll be alvais above the container's content";
container.rawChildren.addChild(label);