If you are on Windows, you can get and set this using WMI (Windows Management Instrumentation). If you google for "wmi screen refesh rates" there are plenty of examples of how to access WMI and manipulate screen parameters. You'd need to write some code to get at the information, though -- there's not a direct way to get at it in MATLAB.
I suspect that for most monitors nowadays, the refresh frequency is 60 Hz.
Setting your display parameters by running an application seems kind of odd, though -- usually you'd expect an application not to do such a thing.