Imports System.Text.RegularExpressions

'Im Konstruktor Sub New bzw. im Load-Event:
  AddHandler TextBox1.TextChanged, AddressOf TxtChanged


  Private Sub TxtChanged(ByVal sender As Object, _
        ByVal e As EventArgs)

    RichTextBox1.ResetText()
    RichTextBox1.Text = TextForRtfBox()
    ListBox1.Items.Clear()
    Label2.Text = ""
    If TextBox1.Text = "" Then Exit Sub

    Dim mc As MatchCollection = MatchCol(TextBox1.Text)
    Dim intL As Integer = TextBox1.Text.Length
    Dim intMcCount As Integer = mc.Count - 1

    For i As Integer = 0 To intMcCount
      With RichTextBox1
        .Select(mc(i).Index, intL)
        .SelectionColor = Color.Blue
        .SelectionFont = New Font(.Font, FontStyle.Bold)
      End With
      ListBox1.Items.Add(" " & """" & mc(i).Value & """" & _
            "  Pos.  " & mc(i).Index & "     Stelle  " & i + 1)
    Next i
    Label2.Text = mc.Count & " Zeichenfolgen " & """" & _
          TextBox1.Text & """" & " gefunden."
  End Sub