IF statement based on dates

Hi everyone

I hope one of the smart cookies on this forum can help. I'm finding this one impossible!

My data is layed out as follows:

Name

Start Date

End Date

Amount

31/01/2013

28/02/2013

31/03/2013

30/04/2013

31/05/2013

30/06/2013

31/07/2013

31/08/2013

30/09/2013

31/10/2013

30/11/2013

31/12/2013

Tony

01/01/2013

31/05/2013

25,000

5,000

5,000

5,000

5,000

5,000

John

01/06/2013

31/08/2013

30,000

10,000

10,000

10,000

What I cannot work out is how to get an IF statement to look at the Start Date and End Date so as to put the figures in the various months above. The amount has to be spread across the month columns based on the start and end date and the only thing I could think of was an IF statement.

Greatly appreciated if someone could help on this formula. It's just too advanced for me.

S