Private Sub UserForm_Initialize()
For i = 1 To Sheets(1).[A65000].End(xlUp).Row
Me.ComboBox1 = Sheets(1).Cells(i, "A") ' on se positionne dans le combobox
If Me.ComboBox1.ListIndex = -1 Then ' Existe t-il?
Me.ComboBox1.AddItem Sheets(1).Cells(i, "A")
End If
Next i
End Sub