How to make a lookup table

Hi,

I am trying to make a look up table between 2 graphs. Graph one has force(Y axis) vs displacement(x axis), while graph 2 has Voltage (y axis) vs displacement(x axis). Through a controller I will be getting the voltage numbers, I want to then map that to the extension and then to the force. The goal is to convert Voltage (x axis) to Force (y axis). Any help with this would be much appreciated.

[dpb]

And what have you tried so far, and where did you have a specific problem/question?