midi elapsed time markers

[Peter Dingley]

I was searching for a way to print out midi elapsed time
 in my score to be able to easily start the midi file
at the location I am currently working on. At the moment
 I write these in by hand but they change as I
make changes to the music in other locations. As far as I
 could see, there is  no way of generating these
values automatically. I was looking  for something like
 rehearsal marks with the elapsed time for the midi
file in minutes and seconds based on the \tempo value,
 for example. Would this be a useful new feature
or does the facility already exist?