The e4x selection expressions are very powerful, but fairly
complicated. Look into the docs. (The docs are fair, but I wish
there were many more examples) Particularly see the "::" operator
and "descendants" method. Those, along with the node and attribute
matching functionality will almost certainly do what you need.
These expressions are similar to XPath expressions if you have any
experience with those.
The expressions almost always return an XMLList which is
easily wrapped into an XMLListCollection, giving you even more