How to complete multiple Ajax calls from one element?

Hopefully I've posted this in the right forum. :)

Here is the synopsis of what I am working on:

I have a webpage that has three blocks, A-B-C, locked in a master/slave/sub-slave style relationship (C is dependent on B, B is dependent on A).

The end-user has the option to modify the information in A via a drop-down menu. Once this happens, the information in A-B-C should be updated, in that order (this being the sticking point apparently).

What I'm wondering at this point, without yet getting into the specific code, is what is the theory that I'm working with here? Is there a term for this kind of structure? The tutorials and examples I have come across only ever discuss single elements (and, incidentally, I don't have a problem getting A to work by itself, without regard to B and C), never, as far as I can tell, parent-child stuff like this.

Perhaps this article might help you:
http://www.devx.com/webdev/Article/28695

Thank you for the tip, but unfortunately that's not the type of article that will sink in with me. I need more fully formed examples. Although, reading through that article does make it plain to me that I don't know nearly enough about the basics of what I'm dealing with.

google for AJAX multiple request - you might find what it will suit for u.