Sub numSEM()
For Ligne = .Range("K" & Cells.Rows.Count).End(xlUp).Row To 1 Step -1
If .Cells(Ligne, 1) <> "" Then
.Range("K" & Ligne).Value = NoSemaineISO(Range("A" & Ligne))
End Sub
Function NoSemaineISO(d As Date) As Integer
NoSemaineISO = Format(d, "ww", vbMonday, vbFirstFourDays)
End Function