Fehler im VBA-Code

Private Sub cmb_UpDate_Click()
Dim i As Integer
Dim Workbook As Workbook
Dim wbName As String
'On Error GoTo errHandler
Application.ScreenUpdating = False
Application.StatusBar = "Dieser Vorgang dauert ein paar Minuten. Bitte Geduld haben..."
Application.DisplayAlerts = False
Application.EnableEvents = False
For i = 1 To Sheets("FILES").Range("A1").End(xlDown).Row
wbName = Sheets("FILES").Cells(i, 1)
Workbooks.Open wbName, 3
ActiveWorkbook.Save
'    Set ActiveWorkbook = Workbooks("AddWS_TEST")
'    Workbooks("AddWS_TEST").Sheets("SumET").Copy Before:=Workbooks(wbName).Sheets(17)
'    Set ActiveWorkbook = Workbooks(wbName)
With Workbooks("AddWS_TEST")
.Activate
.Sheets("SumET").Copy Before:=Workbooks(wbName).Sheets(17)
End With
'Formeln einfügen in das bereits kopierte WS in wbName:
With Workbooks(wbName).Sheets("SumET")
.Range("E3").FormulaR1C1 = "='ET120'!R6C4"
.Range("F3").FormulaR1C1 = _
"=SUMIF('ET120'!R[4]C[-2]:R[35]C[-2],""C"",'ET120'!R[4]C[-1]:R[35]C[-1])"
.Range("E4").FormulaR1C1 = "='ET140'!R6C4"
.Range("F4").FormulaR1C1 = _
"=SUMIF('ET140'!R[4]C[-2]:R[35]C[-2],""C"",'ET140'!R[4]C[-1]:R[35]C[-1])"
End With
ActiveWorkbook.Save
ActiveWorkbook.Close , True
Next i
Application.DisplayAlerts = True
Application.StatusBar = False
Application.EnableEvents = True
MsgBox "Dateien wurden aktualisiert", vbOKOnly
Application.ScreenUpdating = True
Exit Sub
errHandler:
Application.DisplayAlerts = True
Application.StatusBar = False
Application.EnableEvents = True
MsgBox "Beim Update der Datei" & vbCr & wbName & vbCr & _
"ist ein Fehler aufgetreten!", vbCritical + vbOKOnly, "ABBRUCH!"
'ActiveWorkbook.Close , True
End Sub