XL 2013 formule Excel pour soustraire 2 dates

Function AnSemJSDate(ByVal Dt As Date, Optional ByVal Sép As String = "|") As String
   Dim TSpl(): TSpl = ArrayASJ(Dt): TSpl(1) = Format(TSpl(1), "00")
   AnSemJSDate = Join(TSpl, Sép)
   End Function
Function DateAnSemJS(ByVal Z As String, Optional ByVal Sép As String = "|") As Date
   Dim TSpl() As String: TSpl = Split(Z, Sép)
   DateAnSemJS = DateASJ(TSpl(0), TSpl(1), TSpl(2))
   End Function
Function ArrayASJ(ByVal Dt As Date) As Variant()
   ArrayASJ = Array(Year(Dt), WorksheetFunction.IsoWeekNum(Dt), Weekday(Dt, vbMonday))
   End Function
Function DateASJ(ByVal An As Integer, ByVal Sem As Integer, ByVal JS As Integer) As Date
   Dim Dt As Date: Dt = DateSerial(An, 6, 31): Dt = Dt - WorksheetFunction.Weekday(Dt, 3)
   DateASJ = Dt + 7 * (Sem - WorksheetFunction.IsoWeekNum(Dt)) + JS - 1
   End Function

Function ArrayASJ(ByVal Dt As Date) As Variant()
   Dim An As Integer, Sem As Integer, JS As Integer
   JS = Weekday(Dt, vbMonday): Sem = WorksheetFunction.IsoWeekNum(Dt): An = Year(Dt + IIf(Sem = 1, 7, 1) - JS)
   ArrayASJ = Array(An, Sem, JS)
   End Function

Function ArrayASJ(ByVal Dt As Date) As Variant()
   Dim Sem As Integer, JS As Integer, An As Integer
   Sem = WorksheetFunction.IsoWeekNum(Dt): JS = Weekday(Dt, vbMonday)
   An = Year(Dt) + (Month(Dt) = 12) * (Sem = 1) - (Month(Dt) = 1) * (Sem > 50)
   ArrayASJ = Array(An, Sem, JS)
   End Function