Hi cliff6361,
I am not quite sure how you are going to use "this control valve sizing program", or if I understand quite what you mean by "valve sizing program". However, here are some thoughts:
Each valve that you chose will have a Cv number that you need to get from the manufacture. Fisher, for example, in their FirstVue sizeing program includes this, and you are then able to match your Cv requirement to the valve's Cv. I would think that other vendors's sizing program does the same. This would mean that if you plan to buy a Fisher valve, you most likely would want to use their sizing program, and the same for each other valve manufacturer.
On the other hand, if you mean a "valve sizing program" to determine what the required Cv of the valve would need to be, then that is a different type of program. That is almost into the realm of a process simulator/modelling progarm. In this case, you are looking at flowrates, upstream/downstream pressures, including pumping curves etc. to determine the max/norm/min flow conditions to determine the range of Cv for the valve. If this is the case, there are vendors such as Aspen/Hyprotech that sell packages that may meet your needs.
Hope this helps.