Metadata Query - Navigate Without Data

Greetings, I'm interested in learning how to create queries against a cubes metadata. Specifically I'm interested in writing a aquery, using VB, to return a collection of bottom level members relative to a given member name.

Using the MDX Sample appication I can execute the query:

select
Descendants([Customer].[All Customer].[Canada],,leaves) on columns
from Sales

to get the members, however, the query appears to attempt to bring back data, thus is probably an expensive method.

It would be great to understand how to implement a meta data query without have to resort to recursion,

TIA