% Done In A Calender Year

I wish to be able to calculate the % of a particular task that is done in a calender year based on the task start date and duration.

Columns Headings:
A: Start Date
B: Duration (months)
C: End Date (= Start date + (duration * (365/12)))
D: 2009
E: 2010
F: 2011
G: 2012, etc

Examples:
Start Duration End Date 2009 2010 2011 2012 2013 2014 etc
1 Jul 09 12 1 Jul 10 50% 50%
1 Nov 09 12 1 Nov 10 17% 83%
1 Nov 10 36 31 Oct 13 6% 33% 33% 28%

So there are two inputs and the outputs (%'s) are calculated for each year.