This can be done with kitControl math blocks and a little help from excel's Trendline feature. Copy and paste the temperature vs pressure values in to excel. Convert to PSIA and Deg R (curve fitting works better). Create a graph and try the various Trendlines until you get a good fit. I came up with this for R134a. y = 0.00003561 x^3 - 0.01308796 x^2 + 2.12259171 x + 421.11910836 With x = PSIA and a range of 20.7 to 149.7 and y = deg R.