Function MondayOffWeek(annee&, Optional ByVal Lweek& = 1)
Dim D As Date, WekD&, Z&
D = CDate("01/01/" & annee)
WekD = Weekday(D, vbUseSystemDayOfWeek)
D = D - IIf(WekD <> 1, WekD - 1, 0)
Z = CLng(D)
Z = Evaluate("= TRUNC((" & Z & "-WEEKDAY(" & Z & ",2)+11-DATE(YEAR(" & Z & "-WEEKDAY(" & Z & " ,2)+4),1,1))/7)")
MondayOffWeek = D + IIf(Z > 1, 7, 0) + ((Lweek - 1) * 7)
End Function