Counting weeks within a time period

[Nenadd]

I am trying to calculate weeks that a property has been occupied within the 01/Jul/2013 and 30/Jun/2014 only. The properties all have different start and end dates as well as different the rental periods which range from 13 to 52 weeks. I can figure out how many weeks the property was unoccupied before the commencement date, but am struggling to find a way to show the weeks occupied between the two dates mentioned above as the periods all vary and sometimes end before 30 June or go past. Does anyone have any suggestions?

[orange]

What does CommenceDate mean? You might consider OccupancyStartDate, OccupancyEndDate to clarify -- if that's what these fields represent.
Where does this fit in your overall business? Is this a contracted (agreed upon) occupancy? Perhaps you could tell us more of the business rules and processes involved.