[SOLVED]Invoiced days per month

I am trying to help someone with a function and can not figure out what would be best to use. What I have is a start rent date and an end rent date. They want to break down how many days in each month the item was on rent so they have a column for each month. For example say an item was rented on 12/14/08 and returned on 1/12/09. It was rented for a total of 30days 18 days in December and 12 days in January. So I would need a function in each column that would return a 14 in the December Column and a 12 in the January Column. Any help would be greatly appreciated as there are over 350 rows and they are doing the process manually right now and taking several days. Thank you in advance.

Also I just noticed that the date range is currently entered as a text in the format 2008-12-14 so YYYY-MM-DD. Don't know if the text will be a problem.

Just attached an expample. In it I am trying to find a function to fill in the green cells.