I've got a large XML file I'm parsing. 

My first selectNodes statement gets me a list of all elements I want to parse through. 

For each element returned by the first selectNodes statement, I want to run another selectNodes.

The XML might look like this:

```
<A>
    <B></B>
    <C></C>
</A>
<A>
    <B></B>
    <C></C>
</A>

```

I am restrained because I must parse the inner nodes, ie each subset of "A", one at a time. 

The end goal is to do something with each B,C combination, one at at time.