Private Sub Worksheet_Change(ByVal Target As Range)
If Target.Column = 1 And Target.Count = 1 Then
If WorksheetFunction.CountIf(Range("A:A"), Target.Value) > 1 Then
Application.EnableEvents = False
MsgBox "Hola ! Mais t'es fou , j'y suis déja "
Target.Value = ""
Application.EnableEvents = True
Else
Range("A2:A" & Range("A65536").End(xlUp).Row).Sort Range("A2"), xlAscending, , , , , , xlNo
End If
End If
End Sub