Range("C13", "AG" & dl).Select
With Selection.Validation
If Not IsNumber Then
.Add Type:=xlValidateList, AlertStyle:=xlValidAlertStop, Operator:= _
xlBetween, Formula1:="RC,RTT,rc,rtt"
.IgnoreBlank = True
.InCellDropdown = False
.InputTitle = ""
.ErrorTitle = "Erreur de saisie"
.InputMessage = ""
.ErrorMessage = "La valeur doit-être RC ou RTT"
.ShowInput = False
.ShowError = True
End If
End With