Thanks for all the thoughts. This wasn't a 2 minute job I could do immediately as the need arose on the weekend when the dentist was shut. But it was a "do as soon as the dentist is open" job as appointments are hard to get and minimising the number of games my son plays without the mouthguard is obviously important. So on the calendar for 9.00 am Monday is the correct solution for me. I was just being a bit wary of putting non-appointments on the calendar. Tickler wouldn't have worked for me as I don't check it every day.
Thanks again - Michael