Nice, I always enjoy seeing an answer arrive before I do
For anyone who's interested, this key press tracking feature in MediaLab is described in the following post:
www.empirisoft.com/support/showthread.php?t=817
But you are very right about that limitation in the DirectRT meta function. I think it's kind of annoying and will put it on the to-remedy list. Currently, meta functions only kick in between trials. It's because the timing loops within trials are so important, we avoid anything that could disturb them. Consequently, meta functions are assigned a lower priority such that they can only function
between trials. We may have a way to change this in the next version so you can do it either way.