XL 2019 Power Query - Calcul d'une différence entre la 1re et la dernière semaine

let
    Source = Excel.CurrentWorkbook(){[Name="Tableau1"]}[Content],
    GroupBySéjour = Table.Group(Source, {"Séj"}, {{"tbl", each _, type table [Index=nullable number, Séj=nullable text, Semaine=nullable number, DepPh=nullable number, DepCo=nullable number]}}),
    AjtDeltaDepPh = Table.AddColumn(GroupBySéjour, "Delta DepPh", each Record.Field( Table.Min([tbl],"Semaine"),"DepPh")-Record.Field( Table.Max([tbl],"Semaine"),"DepPh")),
    AjtDeltaDepCo = Table.AddColumn(AjtDeltaDepPh, "Delta DepCo", each Record.Field( Table.Min([tbl],"Semaine"),"DepCo")-Record.Field( Table.Max([tbl],"Semaine"),"DepCo")),
    ColSupp = Table.RemoveColumns(AjtDeltaDepCo,{"tbl"})
in
    ColSupp

let
    Source = Excel.CurrentWorkbook(){[Name="Tableau1"]}[Content],
    #"Tri bufferisé" = Table.Buffer( Table.Sort(Source,{{"Séj", Order.Ascending}, {"Semaine", Order.Ascending}})),
    #"Lignes groupées" = Table.Group(#"Tri bufferisé", {"Séj"}, {
                                {"Delta DepPh", each List.First([DepPh]) - List.Last([DepPh]), type number},
                                {"Delta DepCo", each List.First([DepCo]) - List.Last([DepCo]), type number}
                        })
in
    #"Lignes groupées"