Public Class Form1
  Dim Links As New Dictionary(Of String, String)

  Private Sub Form1_Load(ByVal sender As Object, ByVal e As _
     System.EventArgs) Handles Me.Load
    With RichTextBox1
      .Cursor = Cursors.Default
      .DetectUrls = True

      ' Richtext in die RTB aus Ressource holen
      .Rtf = (My.Resources.Linktext)

      ' Wörter einem Link zuordnen
      Links.Add("vb-fun", "http://www.vb-fun.de/")
      Links.Add("Net-Forum", _
        "http://www.vb-fun.de/dotnet/forum/forum.shtml")

      ' Wörter als Links "einfärben"
      Dim Pos As Integer
      For Each KeyWort As String In Links.Keys
        Pos = -1
        Do
          Pos = .Text.IndexOf(KeyWort, Pos + 1)
          If Pos > -1 Then
            .SelectionStart = Pos
            .SelectionLength = KeyWort.Length
            .SelectionFont = New Font(.SelectionFont, _
              FontStyle.Underline)
            .SelectionColor = Color.Blue
          End If

        Loop Until Pos = -1
      Next
      ' Cursor wieder an den Anfang setzen
      .SelectionStart = 0
      .SelectionLength = 0
    End With
  End Sub

  Private Sub RichTextBox1_MouseDown(ByVal sender As Object, _
      ByVal e As System.Windows.Forms.MouseEventArgs) _
      Handles RichTextBox1.MouseDown
    Dim Pos As Integer = _
        RichTextBox1.GetCharIndexFromPosition(e.Location)
    Dim myText As String = RichTextBox1.Text, idx As Integer = -1
    Dim PosPattern() As Char = _
        (" .?!""" & vbNewLine & vbTab).ToCharArray

    ' Positionen suchen
    Dim APos As Integer = _
        myText.LastIndexOfAny(PosPattern, Pos) + 1
    Dim EPos As Integer = myText.IndexOfAny(PosPattern, Pos) - 1
    If EPos = -2 Then EPos = myText.Length - 1
    If EPos > APos Then
      ' Wort unter Mauszeiger zuschneiden
      Dim Ziel As String = myText.Substring(APos, EPos - APos + 1)
      ' Wort in den Links? Wenn ja, Browser starten
      If Links.ContainsKey(Ziel) Then Process.Start(Links(Ziel))
    End If
  End Sub

  Private Sub RichTextBox1_LinkClicked(ByVal sender As Object, _
      ByVal e As System.Windows.Forms.LinkClickedEventArgs) _
      Handles RichTextBox1.LinkClicked
    ' Browserstart bei reinen Links
    Process.Start(e.LinkText)
  End Sub

  Private Sub Button1_Click(ByVal sender As System.Object, _
      ByVal e As System.EventArgs) Handles Button1.Click
    Me.Close()
  End Sub
End Class