Function to interpolate a complex table

[rustbucket11]

I need a function that can take two values and and interpolate the third. The table is attached. I have used these forums to lookup other functions for past projects, but I couldn't find a function that could work with this. Any ideas? I also posted this at http://www.ozgrid.com/forum/showthread.php?t=166410

[shg]

See attached.

[rustbucket11]

Thank you shg. This works great for the pressure values given on the table. I haven't checked for pressure values in between but the entropy values I'm getting look to be incorrect.

[shg]

Yikes, I introduced a bug in neatening up some formulas. Corrected in attachment.

[rustbucket11]

It Works! I checked the outputs values and they are correct. Tables look neat as well. Thanks again.