YTD Cost

Hello,

I need your help developin this formula please.

I have a spredsheet listing the different contracts my department has and their values. Each contract has a seprate start and end date.

For example:
Contract 1 on Row #50 has a contract input date of Jan 12, 2010 and Start date of Jan 1, 2010 and end date of Dec. 31, 2010 with a value of $100,000.00

Contract 2 on Row # 55 has a contract input date of March 8, 2010, Start Date of April 1, 2010, End Date of March 31, 2013 and a value of $500,000.00

I would like to figure out the YTD cost of each contract in a seprate cell.

Using the above example,
contract #1 should return a YTD value of $58,333.33 OR ($100,000.00/ 12 months * 7 months)

Contract #2 should return a YTD value of $83,333.33 OR ($500,000/ 24 months (term of the contract, difference in start and end dates) * 4 months)


Would you be able to help me with this?