Access MovieClip objects


I have a mive clip and in it I have a dynamic TextBox. Now I need to change the text of this TextBox from a button outside the movie clip. I tought I could do this something like this:

   trace("Hello, World");
   myMovie.txtTextArea.text = "Hello, World";

the trace tag I did appears correctly, however the text in the movue clip does not appear. Not that ‘MyMovie’ is the instance name i gave to the movie clip. I tried giving the real name but still did not work!

does anyone know how this can be done?