Get Rows and Count from user selected Area (by cursor)

Following code used to work in earlier Versions of EXCEL:

Sub RechnungErstellen()
   Mappe = ActiveWorkbook.Name
   RufBlatt = ActiveSheet.Name
   With Application.ActiveWorkbook
      With ActiveSheet
         zo = ActiveCell.Row
         i = Selection.Rows.Count       ' <-- causes run time error
                                                    ' Run-time error '-2147319784 (80028018)': 
                                                    ' Method 'Selection' of object failed
         zu = zo + i - 1
         For z = zo To zu
            RgDat = .Cells(z, 1)
            Rechnung_Initialisieren
            Posi_in_Variable
            ActiveWindow.SelectedSheets.PrintOut Copies:=1
         Next z
      End With                            ' ActiveSheet
   End With
End Sub

Can anybody help?