Sub Sommes()
Dim tablo, ub&, col%, lig&, i&
tablo = Intersect(Sheets("base").[C8:IV65536], Sheets("base").UsedRange)
ub = UBound(tablo)
For col = 1 To UBound(tablo, 2)
For lig = 1 To 3
For i = lig + 3 To ub Step 3
tablo(lig, col) = tablo(lig, col) + tablo(i, col)
Next
Next
Next
With Sheets("resultat")
.[D6:IV8].ClearContents 'RAZ
.[D6].Resize(3, UBound(tablo, 2)) = tablo
.Activate 'facultatif
End With
End Sub