Shared Library Symbol and AS3 Class Linkage

I have created a symbol that imports a movie clip from another FLA/SWF (MovieClip, Property, Import for Runtime Sharing). It imports all right, but, I would also like that imported MovieClip to have its own class and have it be aware of any instances within it.

So, for example, the imported MovieClip is named: CSceneWinLose. I created a class file and have the linkage class name matching:

public class CSceneWinLose extends MovieClip
  //normally, you extend the library item, in my case named BMCSceneWinLose.  
  //This is what I want! But it is not aware what BMCSceneWinLose is.
   public function CSceneWinLose():void
      winScreen.visible = true; //By extending MovieClip, cannot compile because it doesn't know what winScreen is.

How does one access the items (instances) inside of a imported movie clip? I feel like I should have to extend BMCSceneWinLose in my example, but in order to do that, I should import something.

A quick response would be very deeply appreciated.