There was some discussion of this. I'll have to experiment. One issue is that I don't have access to screen reader software, so I rely on hearsay a lot. I know that there is a time-bombed demo of JAWS, but I'm waiting until the site has been developed further before I start the ticking.
We had an issue detecting a print rendering (I don't remember the thread well enough to call it up, but someone wanted to change content, based upon its being read for printing).
I think the consensus was that it can't really be done. I don't know if this would be bound by the same restrictions.