This must be the week for complaining about Outlook’s recurrence patterns. No, Outlook does not offer every 5th week pattern. This is because not every month has a 5th week and Outlook won’t know what to do those months. Instead, it offers a ‘last week’ option. It doesn’t have a quarterly pattern but you can make you own – every 90 days, 13 weeks, or 3 months.

If you need more configurable recurrence patterns, try WS:Repeat Appointment. It can even do recurrences which aren’t patterns.

WS:Repeat Appointment
http://www.websetters.co.uk/WSAddIns/WSRAII/index.htm