' ermittelt aus einem Datum die Kalenderwoche
Public Function kw(ByVal d As Date)
Dim t As Long
    t = DateSerial(Year(d + (8 - WeekDay(d)) Mod 7 - 3), 1, 1)
    kw = ((d - t - 3 + (WeekDay(t) + 1) Mod 7)) \ 7 + 1
End Function