Scratching at a Master meet

I am considering scratching an event at an upcoming meet. Is there a protocol that I should be aware of. For instance, at a USA meet, if you fail to report to the blocks for event A, you are automatically DQ'd for event B. Is this true in USMS as well? I would like to make a "game time" decision, but it's the 2nd event that I'd like to focus on, and would be totally bummed if I screwed up.