Sub testa()
Dim Vcellule As Range
Dim Vligne As Long
Dim Feuille As Worksheet
Set Feuille = Sheets("Feuil1")
Set Vcellule = Feuille.Range("A5:C" & Range("a5:a65536").End(xlUp).Rows)
For Vligne = 1 To Vcellule.Rows.Count / 3
If Vcellule.Cells(Vligne, 1).Value = "d" Then
Vcellule.Cells(Vligne, 3).Value = 16
End If
Next Vligne
End Sub