Dynamic text in movieclip nested in buttons.

Hello...

I'm trying to access a dynamic textbox nested inside a movieclip, which in nested inside a button. Now I can't seem to get access to the movieclip through the button...
So how can I change the text inside the movieclip nested in the button?

Normaly I would like this:
buttonInstanceName.MovieclipInstanceName.TextboxInstanceName.text = "Text has now been changed";

But this doesn't work. However without the movieclip being nested in the button it works fine:
MovieclipInstanceName.TextboxInstanceName.text = "Text has now been changed";

What am I doing wrong?

regards
  Bjarke