Hi @jmh9 ,
I don't know the exact answer to your question but have a couple of suggestions.
If you are using New Quizzes, you can select "Require a student access code." If you give out the code orally in class, absent students won't be able to take the quiz.
For either Classic or New Quizzes, you can use Module Requirements to unlock the quiz. Set up a Module for the quiz but put two quizzes in it. The first quiz is set as the requirement for the second one, and you will give the answer to the first quiz live in class. That will allow students who are in class to then unlock the second, real quiz.
I hope one of these suggestions will work for you.