IXMLDOMNodeListPtr problem pls help

I have a IXMLDOMNodeListPtr, and I want to take each node, and look through the child nodes, getting one value and setting another.

ex:

<e1>
<e2>value2</e2>
<e3 />
</e1>
<e1>
<e2>value2</e2>
<e3 />
</e1>

I then want to for each e1:
Get value of e2
Set value of e3

How to do that?

Thanks in advance