I'm Not Getting A Basic AS-3 Principle

I Don’t Get A Basic AS-3 Principle

I’m attempting to do my first AS3 project.

I’m missing something HUGELY obvious.

I got my separate classes in separate .as files.

In one of my classes I wait for a text file to load and then call a function.

HOW do I pass the resulting value back up to the main time line?
HOW do I get my main timeline to know that the event has fired, and it can do the next thing?

Let me ask the question another way:

In my perhaps personal and warped sense of structured programming, I send requests down,I get data back, and I then advance to the next step.
In all of the examples I’ve seen of AS-3, it seems to be build on ever more concentric layers of classes within classes.

Is the ideal for an application to be a single instance of a class?
How do I have modular code, if I can’t combine the results from several classes in some sort of central place?