Fifth Sunday

Our church has different services on the first and third Sundays of each month, and regular services on all other Sundays. I can’t figure out how to get an event to repeat on more than one nth day a month (second, fourth and fifth), so I’m adding the services for each of those weeks as separate events. The trouble is that I can’t seem to be able to add a service on the fifth Sunday of the month. I know they don’t happen often, but they do occur, and I don’t want it to suddenly look as if there’s no service that week.

Anyone know how to get a fifth Sunday working?