Sub foutuePluie()
Dim tabRes()
tablo = [A6].Resize(Cells(Rows.Count, 1).End(xlUp).Row - 5, 2)
nbLig = Cells(Rows.Count, 1).End(xlUp).Row - 5
ReDim tabRes(nbLig, 0)
first = True
For lig = 1 To UBound(tablo)
If tablo(lig, 2) > 0 Then
For recul = lig - 1 To 1 Step -1
If first Then tabRes(lig - 1, 0) = tablo(lig, 2) / (tablo(lig, 1) - tablo(1, 1)): first = False: Exit For
If tablo(recul, 2) > 0 Then tabRes(lig - 1, 0) = tablo(lig, 2) / (tablo(lig, 1) - tablo(recul, 1)): Exit For
Next recul
Else
tabRes(lig - 1, 0) = 0
End If
Next lig
Cells(6, 5).Resize(UBound(tabRes) + 1, 1) = tabRes
End Sub