Hello Justmcd
My maths isnt bad but Ive never been brilliant with graphs unless they are very basic. Ive had a look and I (sort of) understand what interpolation is.
I also read that Excel doesn't have an Interpolation function but they also explained how to create one (probably using the UDF route).
Take a look at this link and see if its any help. Let me know how you get on.
http://www.blueleafsoftware.com/Prod...ationExcel.php
HTH
Hercules
Bookmarks