Error 1120: Access of Undefined Property parent + movieclip(parent)

I am trying to access a function that is on my document class for my AS3 project, from a nested class. That is, the Document Class calls Class A which then calls Class B. So I am trying to access a function from Class B, I am trying to use MovieClip(parent).function(); but I am getting error 1120. The MovieClip(parent) (fixed to reflect my document class, etc) works when I try it from other classes but not from this nested class. Any ideas would be greatly appreciated.