Public Function updateNodo(ByVal padre As String, ByVal nodo As String, ByVal attr As String, ByVal newval As String) As String
...
Dim root As XmlElement = doc.DocumentElement
      node = root.SelectSingleNode(nodo)
      Dim str As String
      For Each a In root.ChildNodes
        If a.Name.Equals(padre) Then
          node = a
          For Each b In node.ChildNodes
            If b.Name.Equals(nodo) Then
              b.Attributes(attr).Value = newval
              modified = True
            End If
          Next
        End If
      Next
...