[Orgmode] Monthly events based on count of specific weekdays

[Ben Finney]

Howdy all,

How can I set an event in Org mode that repeats every month, on a
specific weekday, on a week counted from the start of the month?

For example:

  * every month on the first Tuesday of the month.
  * every month on the third Sunday of the month.
  * every first and third Wednesday of the month.

Taking “first Tuesday of the month”, if I set it this month on
<2009-11-15 Sun>, it should next repeat on <2009-12-20 Sun> and so on
each month. These do not do what I want:

  * <2009-11-15 Sun +1m>
  * <2009-11-08 Sun ++1m>
  * <2009-11-08 Sun .+1m>

    Each of these next repeats on <2009-12-15 Tue>, the wrong date.

How can I specify a repeating event to Org mode that achieves what I
described above?

-- 
 \     “Nature is trying very hard to make us succeed, but nature does |
  `\       not depend on us. We are not the only experiment.” —Richard |
_o__)                                   Buckminster Fuller, 1978-04-30 |
Ben Finney