Sub test()
Dim k%, i%, nbcelnonvide%, somme%
For k = 1 To 15
With Sheets(k)
For i = 2 To 22
somme = somme + .Cells(i, 2).Value
If IsEmpty(.Cells(i, 2).Value) = False Then nbcelnonvide = nbcelnonvide + 1
Next i
If somme <> 0 And nbcelnonvide <> 0 Then .Cells(23, 2).Value = somme / nbcelnonvide
somme = 0
nbcelnonvide = 0
End With
Next k
End Sub