I forgot to reply to your last question.
I guess I don't need to hide the slides of students who are absent, but I can't think of another way to omit their slides from the randomizer on days they are absent.
We will use the randomizer quite often, and if it's jumping to students who aren't present half the time then it will be really lagging on our tempo/efficiency.

Is it possible to randomly select from a range of objects (ie. objects that are hyperlinks) but not randomize those objects that are hidden? Perhaps this angle of approach would be easier.