Sub Worksheet_Change(ByVal Cible As Range)
Application.EnableEvents = False
If Not Intersect(Cible, Range("A1")) Is Nothing Then
Range("B1").Value = Range("A1").Value
End If
If Not Intersect(Cible, Range("B1")) Is Nothing Then
Range("A1").Value = Range("B1").Value
End If
Application.EnableEvents = True
End Sub