Maybe someone can help me out with a problem.

I'm looking for a method of creating a formula that will calculate the data in this chart with only the first and last values entered. This chart is a sample of one that will calculate performance figures for an aircraft engine. the actual chart will require calculation of a couple of thousand figures.

Thanks.

Tim.

-1000 -750 -500 -250 0 250 500 750

-2 26.75 25.25

-1

0

1

2

3

4

5 26.25 24.75