Clickable phone number with pauses and bridge/extension in calendar event
I found this thread: http://forums.androidcentral.com/verizon-galaxy-s-iii/297744-calendar-event-how-add-bridge-numbers-easy-dial.html

It looks like you can make a contact with a complex dialing code and then link to that contact as an attendee on the calendar event. Then click the attendee link to dial the number.