I recommend you to use Engineering Equation Solver. The major feature that distinguishes EES from other equation solving programs, however, is its extensive library of built-in functions for thermophysical properties. Thermodynamic and transport properties of steam, R22, R134a, R407C, air, ammonia, carbon dioxide, and many others are implemented in a manner such that any independent set can be used to determine the remaining unknown properties. EES has an extensive library of built-in functions, but it is not possible to anticipate the needs of all users. A remarkable feature of EES is that the user can add (and later remove) functions and procedures written in any compiled language, such as Pascal, C, C++ or FORTRAN. These external routines may have any number of arguments. Functions return a single value whereas procedures may return multiple values. The external routines are used in exactly the same manner as internal EES subprograms. This capability gives EES unlimited flexibility and it is among its most powerful features. External functions and procedures can provide the units of their inputs and output so that EES can check units when they are called. They can also issue error messages (which stop the calculations) or warning messages that are displayed after the calculations are completed.
You can use CoolProp (www.coolprop.org), it is an open access library for computing thermophysical properties of pure, pseudo pure and mixtures fluids. You have wrappers for many different modeling environment, including Matlab. To me, it is your best option.
I would recommend CoolProp (http://coolprop.sourceforge.net/coolprop/wrappers/MATLAB/index.html#matlab) since it can also be coupled with REFPROP. This way you can take advantage of both property libraries.