Hi Don,
What you are trying to accomplish is definitely possible, and can be accomplished in a variety of ways. I have the following recommendations:
1) Your sequence file should ideally be written in a way that it can run from any operator interface (not just your custom interface). Though it is possible for you to set global variables from your operator interface, I would actually recommend avoiding this so that your operator interface and sequence file are less interdependent.
2) The shipping example code for the CVI TestStand operator interface should help to get you started with developing your custom interface. This example can be located at (C:\Program Files\National Instruments\TestStand 4.0\UserInterfaces\NI\Simple\CVI). In specific, the example shows exactly how to implement a run button that executes your sequence with a certain entry point, and how to implement a terminate button as well.
3) To set a variable in order to run your sequence in "burn in" or "vibration" mode, I would recommend either using a TestStand popup window, or calling a CVI dialog from TestStand. The main idea here is that setting variables in order to control execution makes more sense during run-time, and can happen independent of the operator interface being used.
I hope this helps. Please let me know if I can clarify anything above and I would be glad to help you further. Have a great day Don!
Regards,
Casey Weltzin
Applications Engineer
National Instruments