putting xml result into a listbox

i am being returned an xml string from a webservice call

when i get the result i'm doing this

XmlDocument doc = new XmlDocument();
doc.Load(new StringReader(xmlresult));

i then have <asp:ListBox id="results" runat="server"></asp:ListBox>

Is anyone able to show me how i populate the ListBox with the xml and a for loop?

I've googled but can't find a relevant example

The xml is like this

<?xml version="1.0" encoding="UTF-8"?>
<Top>
 <Level1>
  <Level1Detail>
   <Id>xxx</Id>
   <email>xxx@xxx.com</email>
   <from>xxx@xxx.com</from>
   <subject>xxx</subject>                  
  </Level1Detail>
 </Level1>
etc...
</Top>