Here's a small example, from a thread I posted a day or two ago:

VB Code:
  1. Dim XMLDoc As New XmlDocument
  2.         Dim XMLN As XmlNode
  3.  
  4.         XMLDoc.Load(Server.MapPath("family.xml"))
  5.  
  6.         Dim XMLNL As XmlNodeList = XMLDoc.SelectNodes("//family/name")
  7.  
  8.         For Each XMLN In XMLNL
  9.  
  10.             If XMLN.ChildNodes(0).InnerText.ToUpper = "Alfred E".ToUpper Then
  11.                 XMLN.ChildNodes(0).InnerText = "What me worry"
  12.             End If
  13.  
  14.         Next
  15.  
  16.         XMLDoc.Save(Server.MapPath("family.xml"))

Does this help?