Public Class Form1
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button1.Click
        Dim txt As String = "Teil1, Bemerkung: Teil2"
        Dim was As String = "Bemerkung: "
        Dim pos As Int32 = txt.IndexOf(was)  ' Suche die Position von was in txt
        If pos > -1 Then                      ' wenn gefunden dann
            pos += was.Length               ' addiere die Länge 
            MsgBox(txt.Substring(pos))      ' und zeige den Text ab dieser 
            ' Position an
        End If
    End Sub
End Class