Having a sub swf dispatch an event to the parent swf?

I’m having a major issue wrapping my head around another developers way of dispatching events.

What they have now is:

subswf.fla
-Class A instantiated
-Class B instantiated

Class B has a function that dispatches CustomEvent.
On the timeline of subswf, i attach the listener to ClassB and provide a handler.
The handler calls a method in Class A.

I want to also be able to call a method in the parent swf’s instantiated Class C.

Any ideas or recommendations please?