try this. it's a recursive search:

vb Code:
  1. Private Sub SearchTree(ByVal startNode As TreeNode, ByVal sSearchString As String)
  2.     If startNode.Text.Contains(sSearchString) Then
  3.         startNode.ForeColor = Color.Red
  4.     Else
  5.         startNode.ForeColor = Color.Black
  6.     End If
  7.     For Each n As TreeNode In startNode.Nodes
  8.         SearchTree(n, sSearchString)
  9.     Next
  10. End Sub