If your picture is your entire block diagram, then you have a problem. There is no loop to wait for user input. When you run it, the OK and Cancel buttons will be read once. OK will be false when it is read because you don't have time to click on it before it is read. So the False case will execute and then the program ends. You will not be able to do anything. The code must go inside a While Loop with either the OK or Cancel button wired to stop the loop.
Also, the Cancel button is wired to a Labview Stop function. This is a bad way to stop the code. Don't use the Stop function, just let the code stop naturally. With a loop, either button can be made to stop the loop, and then the program will end naturally because there will be no more code to execute.
