[O] org-habit for multiple arbitrary days in a week

[James Harkins]

I have a task that I want to track using org-habit. I've spent about an hour 
looking through the manual and other sites, but so far the problem remains 
intractable.

With org-habit, it's easy to track something that should be done on one 
particular day of the week: .+1w.

It appears not to be easy to track something that should be done on two 
arbitrary days of the week.

It's easy to schedule something for two specific days of the week using a sexp. 
But, org-habit (for sensible reasons) doesn't support sexps.

I can also add multiple SCHEDULED lines. But org-habit doesn't work well with 
this either.

** TODO Update lesson gradesheet                                               
:Comp:
   SCHEDULED: <2014-10-13 Mon +1w>
   SCHEDULED: <2014-10-17 Fri +1w>
   :PROPERTIES:
   :STYLE:    habit
   :LOGGING:  TODO MAYBE INPROG MTG | DONE(!) POSTPONED
   :END:

Now, if I mark this item DONE, org-habit moves *both* scheduled dates forward 
to next week, even though 10-17 is still in the future and it's neither needed 
nor desirable to advance it. That is, scheduled dates that are today or in the 
past should move up, while scheduled dates in the future should be left alone. 
I guess the issue with that would be that you couldn't set a task DONE earlier 
than scheduled. That's not an issue for this specific task, but maybe for 
others.

I suppose the worst case is that I could create two "Update lesson gradesheet" 
entries, but that seems highly inelegant...?

Thanks in advance for any advice.

hjh