Time Difference between Documents

I've done some searching, and best I can find is that this isn't possible..

We have logs that we are storing, and some of the logs indicate transactions take place as users step through the site.
We would benefit from being able to take a transaction ID, track it through the system, and calculate time spent at each step.
This would end up looking like.. For example..
3 Documents

  "step": "1",
  "timestamp":"2016-09-13 10:00:00.000"

  "step": "2",
  "timestamp":"2016-09-13 10:30:00.000"

  "step": "3",
  "timestamp":"2016-09-13 11:30:00.000"

We have a Dashboard created that lets us plug in a transactionID and lets us view different stats for all the docs related to that transactionID.
We would like to be able to calculate times between different steps.. In this example, 30 mins between step 1 and step 2, and then an hour between step 2 and step 3.

Is this possible?

serial_diff might work for you.