What it does:

  `bzg-step-time-report-initialize' will prompt for the name of the
  project. This headline have a property called "Elapsed_time". It's
  computed when you switch to the column view (C-c C-x C-x) or when you
  press C-c C-c in front of it.

  `bzg-step-time-report-add-step' will update the `Elapsed_time' value
  of the previous headline and insert a new one.

  `bzg-step-time-report-finish' will just update the `Elapsed_time'
  value of the previous headline.


Of course, this could be refined... but I hope it might help!

Regards,

PS: You might also have a look at the `run-at-time' function, but either
you need to get the time intervals between steps, or you need to know on
what frequency they are inserted, right? See (info "(elisp)Timers")

-- 
Bastien