Dim tn As TreeNode
 Dim Unterverzeichnis As New IO.DirectoryInfo(DerPfad)
tn.Tag = Unterverzeichnis.FullName ' Hier wird der Pfad gespeichert

Private Sub treeview1_BeforeExpand( _
  ByVal sender As System.Object, _
  ByVal e As System.Windows.Forms.TreeViewCancelEventArgs) _
  Handles TreeView1.BeforeExpand
 
  Dim tn As TreeNode
   tn = e.Node
 
Dim Pfad as String = tn.Tag.toString
Msgbox (Pfad)
 
End Sub