Private Sub Worksheet_Change(ByVal R As Range)
Set R = Intersect([A:E], UsedRange)
If R Is Nothing Then Exit Sub
Dim tablo, ub%, i&, j%
tablo = R.Resize(R.Rows.Count + 1).Value2 'matrice, plus rapide, au moins 2 éléments
ub = UBound(tablo, 2)
For i = 1 To UBound(tablo)
For j = 1 To ub
If CStr(tablo(i, j)) = "0" Then tablo(i, j) = "null"
Next j, i
Application.EnableEvents = False 'désactive les évènements
R = tablo
Application.EnableEvents = True 'réactive les évènements
End Sub