Private Sub UserForm_Initialize()
Dim MonDico As Object, C As Range, R$
Set F = Sheets("Users")
R$ = "$A$2:" & F.Range("A" & Rows.Count).End(xlUp).Address
Set MonDico = CreateObject("Scripting.Dictionary")
For Each C In F.Range(R$) '******cette ligne*****
MonDico(C.Value) = UCase(C.Value)
Next C
Me.ComboBox1.List = MonDico.items
End Sub