Sub formule()
Dim h As Long
With Sheets("Grille_de_Disp")
.Protect "2580", UserInterfaceOnly:=True
h = .Range("A" & Rows.Count).End(xlUp).Row + 1
.Range("P2:P" & h) = "=SUMIFS(H$2:H$" & h & ",A$2:A$" & h & ",A2,B$2:B$" & h & ",B2,C$2:C$" & h & ",C2)"
End With
End Sub