Create the subsummary report in course bookings. If you dont want the detail, you can delete out the BODY part. Keep in mind that the report will reflect your found set so you may want to preface it with a show all if reporting for all the records. Also also keep in mind that the subsummary report has to be sorted by the break field ( courseID I would assume ) and in preview mode.
Thanks for getting back to me. I've created a subsummary layout in the course bookings database and I'm using the course title (each one is unique) as the break field, but I'm still not sure which field would provide a sum of all participants booked onto that course. Would I need to create a new field and if so, what type of field?
Sorry for being slow on this one, but I've never had to set up subsummaries before and it's causing me a bit of bother!
Create a subsummary field for counts of course title.