Sub Une_ligne_sur_deux_colorer_2()
Const LstCol As Integer = 7 ' Dernière colonne
Dim i As Long, Plg As Range
Set Plg = Range(Cells(2, 1), Cells(2, LstCol))
For i = 4 To Cells(Rows.Count, "a").End(xlUp).Row Step 2
Set Plg = Union(Plg, Range(Cells(i, 1), Cells(i, LstCol)))
Next i
Plg.Interior.ColorIndex = 34
End Sub