if I understand correctly you have data as follows:
With X in column A and Y in column B
A B
1 3.2 9.1
2 120.1 171.7
You want to know what the value of Y is if, say, X=4.7
Mathematically you would use:
(4.7 - 3.2)
----------- x (171.7 - 120.1) = (0.2542) x (51.60) = 13.12
(9.1 - 3.2)
Add this to the first Y value 120.1 + 13.12 = 133.22
In this example, try:
A B
1 3.2 9.1
2 120.1 171.7
3
A4=4.7
A5=A1 + (A4-A1)/(A2-A1) x (B2-B1)
This is two cells but you need FOUR data points.
