Problem mit Combobox sortieren

Private Sub UserForm_Initialize()
'Combo füllen
Dim ws As Worksheet, iRow As Long, col As New Collection
Set ws = Sheets("Produktion")
iRow = 2
On Error Resume Next
Do Until IsEmpty(ws.Cells(iRow, 6))
col.Add ws.Cells(iRow, 6), ws.Cells(iRow, 6)
If Err = 0 Then
cmbSparte.AddItem ws.Cells(iRow, 6)
Else
Err.Clear
End If
iRow = iRow + 1
Loop
'Combo sortieren
Dim iLast As Integer, iNext As Integer, iTmp As Integer
With cmbSparte
For iLast = 0 To .ListCount - 1
For iNext = iLast + 1 To .ListCount - 1
If .List(iLast) > .List(iNext) Then
iTmp = .List(iLast)
.List(iLast) = .List(iNext)
.List(iNext) = iTmp
End If
Next iNext
Next iLast
End With
End Sub