Breaking the number of days between start and end dates to months

I need to track days for beds by Month. I have a Start Date and End Date. If the datediff days spans multiple months I need to attribute the days to the proper months. The report will run monthly and the beds need to report the number of days for that month

Example :

Start Date 12/15/2012 to End Date 3/15/2013
Dec - Jan - Feb - Mar
16 - 31 - 28 - 15

So if I run the report in Feb the bed days count will = 28

Hope this makes sense

I am using Crystal 2008 BO