Right now, the way your program is organized, the Property node which changes the Y-scale is executed once, and then you wait in a while loop until the user presses Print or No Print. If you want the user to be able to change the Y-scale while you are waiting for one of the Print buttons to be pressed, then you need to place the property node which changes the Y-scale values inside that same while loop. If you want to see what is happening inside your code, click on the "Light Bulb" from the block diagram to enable "Highlight Execution" and run your VI to watch how the functions in your VI are executed.
