I don't think that you properly implemented Jimmy's Whichweek function

[vba]

Function WhichWeek(Cell As Range) As Long
Dim Ref As Date, RefWeekDay As Long

Ref = CDate(Year(Cell.Value) & "/" & Month(Cell.Value) & "/01")
RefWeekDay = Weekday(Ref, vbSunday)

WhichWeek = (Day(Cell.Value) + RefWeekDay - 2) \ 7 + 1
End Function
[/vba]