How can i insert a new node after an element which contains specific text?

I have an xml document -

<?xml version="1.0"?>
<mstns>
<curves id="curve0">
</curves>
<classification name="ROUND STN STL BAR">
<material name="DIA 3MM STN STL 316 h9">
</material>
</classification>
<classification name="ROUND STN STL BAR (FOR BENDING)">
</classification>
</mstns>

I want to insert a new node
<material name="test1">
</material>
after the node <classification name="ROUND STN STL BAR (FOR BENDING)">

but the node to insert after will be selected in a listbox.

please help as i'm new to VB and have spent several days looking for a solution to this. The rest of my program works :-)

thanks