Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
  System.EventArgs) Handles Button1.Click
        Dim dialog As PrintPreviewDialog = New PrintPreviewDialog()
        Dim doc As Printing.PrintDocument = New Printing.PrintDocument()
        dialog.Document = doc 'Ohne Zuweisung erhält der Dialog immer den Fokus
        dialog.Show()
End Sub