Bonjour,
Pour éviter de planter Excel, prendre quelques précautions.
Private Sub Worksheet_Change(ByVal Target As Range)
If Target.CountLarge > 1 Then Exit Sub
If Not Intersect(Target, Range("C:D")) Is Nothing Then
Application.EnableEvents = False
Target.Value = UCase(Target.Value)
Application.EnableEvents = True
End If
End Sub