Paul,
I'm not sure how you want your code to works. This looks like a "Weighing" task, where pushing Tare saves a single result that serves as a "Tare", to zero (by being subtracted from) subsequent Weighings. It is unclear what you want to happen if Tare is never pushed, or if Tare is pushed 17 times. Similarly with Start -- what if it is never pushed, or pushed 5 times? Stop is clearer ...
Look at the Tare case. You know you've got Tare from the Queue (as you are in the Tare case), so comparing it with itself will always be True.
You should need only two loops. One loops handles your Events (button pushes, with all of your buttons being proper Latch When Released, especially Stop), and the other your QMH. Think about how you might have another message ("Sample") that does the AI Read. You might need to know what "State" the system was in, i.e. "Has Start been pushed?", "Has Tare been pushed?", and act accordingly (see questions in first paragraph).
Bob Schor
