Hi

This function may be of help.
I assumed that 1st day of the week is Monday, you may want to change that. Also, in the line highlighted in red, you might have to change the whole expression, because of regional settings. (I'm not sure about the latter.)
[vba]Function WhichWeek(Cell As Range) As Long
Dim Ref As Date, RefWeekDay As Long

Ref = CDate(Year(Cell) & "." & Month(Cell) & ".1")
RefWeekDay = Weekday(Ref, vbMonday)

WhichWeek = (Day(Cell) + RefWeekDay - 2) \ 7 + 1
End Function
[/vba]
By the way, a month can span over 6 weeks even, like this July, so count on 6 new sheets instead of 5.
See the attached example.

Jimmy