Private Sub Workbook_SheetChange(ByVal Sh As Object, ByVal Target As Range)
Dim i&, j&
If Not Intersect(Target, Sh.Range("A4,A6,A8,B4,B6,B8")) Is Nothing Then
On Error GoTo ERR001
Application.EnableEvents = False
For i = 2 To Worksheets.Count
For j = 4 To 8 Step 2: Worksheets(i).Cells(j, "a") = Worksheets(i - 1).Cells(j, "b"): Next
Next i
End If
ERR001:
Application.EnableEvents = True
If Err Then MsgBox "Erreur n° " & Err.Number & vbLf & Err.Description
End Sub