create future costs by the help of a functions from a other sheet

Hello Excel fans,

i have a good idea, how to create future costs on contracts.

I just donīt know how to do that in Excel.

Each contract has a startdate and a enddate.


In the table i have the columns year and sum costs.

I put the file in the Appendix.

startdate: 01.08.2009
enddate: 31.07.2017

year amount

08/2009 - 12/2009 0
01/2010 - 12/2010 1615
01/2011 - 12/2011 16000
01/2012 - 12/2012 44000
01/2013 - 09/2013 54000

Now i have a Diagramm which Show a function.

The costs proceed in average like this. Can exel create me somehow a function?

Or can Excel calculate the expected costs with the help of the Diagramm?

Right now the contract runs 5 years and 1 months, this is 40% of total costs.

So still 60 percent of the costs are missing.

Do you know what i mean?

Can someone help me?