Calculate number of months in year

Hi,

I would like to calculate the number of months in a period such as 2012 dependant on a start and end date. The attached spreadsheet has an example of this but basically i need:

Start Date = 01/08/2011
End Date = 31/05/2012
Calc should be = No. of months in 2012 = 5

I need this to work for any start and end date criteria.

As always many thanks for your help