Extending a movieClip

Does flash allow for actual derived classes of movieClip? I got an error when I tried to do this: (I’m making a better listBox for flash :slight_smile: )

class DynamicListBox extends MovieClip
{
    function DynamicListBox(){
    this.onEnterFrame = function():Void{ trace("Hello");}
    }
};

I mean doesn’t extend inherit the property and functions of MovieClip? Or does flash not handle it like this?