Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) _
  Handles Button1.Click
    Teil(0) = "AA"
    Teil(1) = "BB"
    Teil(2) = "CC"
    Teil(3) = "DD"
    MessageBox.Show(Ergebnis)
    Teil(1) = "XX"
    MessageBox.Show(Ergebnis)
    ergebnis = "AAZZCCDD"
    MessageBox.Show(Teil(1))
End Sub
 
Private Teil(3) As String
Property Ergebnis() As String
    Get
        Return String.Join("", Teil)
    End Get
    Set(ByVal value As String)
        Teil(0) = value.Substring(0, 2)
        Teil(1) = value.Substring(2, 2)
        Teil(2) = value.Substring(4, 2)
        Teil(3) = value.Substring(6, 2)
    End Set
End Property