Accessing an instance of a symbol from AS3

Hi… I have a symbol (of type movie clip) which is exported for action with AS3 as, say clsAux. From an AS file, I extend this class to program some methods to interact with it
The movie clip has, inside, an instance of another symbol, and the instance is called objAux2.
The problem I have is that, from code, from the class which is extending clsAux, I can’t figure out how to access objAux2.
I have tried, from clsAux, to make the movie clip gotoAndStop the frame where objAux2 is instantiated (where the keyframe where it is created is) and then access it like this.objAux2 (error), this[objAux2] (error)… is there any way I can access the instance of a symbol from code?
Thank you…