Sub Traitement()
Dim DernLig As Long, L As Long
Application.ScreenUpdating = False
With Sheets('Feuil1')
DernLig = .Range('A65536').End(xlUp).Row + 1
For L = DernLig To 3 Step -1
.Rows(L - 1 & ':' & L).Insert Shift:=xlDown
Next L
End With
Application.ScreenUpdating = True
End Sub