Private Sub Worksheet_Activate()
Dim r As Range, n As Byte, v As Variant
Application.ScreenUpdating = False
On Error Resume Next 'si aucune SpecialCell
Cells.Delete 'RAZ
Sheets("PL").[A:K].Copy [A1]
Set r = [G:G].SpecialCells(xlCellTypeBlanks)
For Each r In r.Areas 'plages vides
If r.Row > 1 Then
For n = 3 To 4
v = r(0, n) 'colonne I puis J
If IsNumeric(CStr(v)) Then r(0, n).Resize(r.Count + 1) = v / (r.Count + 1)
Next n
End If
Next r
End Sub