You have been so kind to me, that I was originally going to say "No", don't bother, I will just try harder to remember in future.
But I then felt that it might be more useful to accept it, and tell you how it works, in case it is worth adding to the product itself.
After all, it is really only of any use to someone who knows how to add the relevant message.
So the first question is ... if you add the alert message, would that involve you in getting questions about what it means, because those who don't know might think it was a useful feature, and that sticks you with having some enforceable policy.
So I'll say yes in case (a) it is actually useful; and (b) you think of some way of incorporating it into PM without increasing your own overhads.
I have classes to teach from now until the evening so today (Monday) is out; and I have classes to teach until 1:00 pm tomorrow, so any time Tuesday afternoon is fine. However, Wednesday is probably the best bet as I am free all day.