Hi jazzman1,
Thanks for your response.
I was more looking at the subset or intersection of the the three rows where the End Time of all the rows do not exceed the End Time of the first row.
Actually my initial calculation of 85 seconds is incorrect. I believe it should be 40 seconds.
Here is my logic:-
From the first row the duration is 00:02:54 or 174 seconds.
The second row the Start and End time falls within the first Start and End and the duration is 49 seconds and is the total subset time used at this time.
The third row starts within the second row but ends after the second row so the duration will be a difference of 2013-10-08 08:32:06 and 2013-10-08 08:32:46 which is 40 seconds.
I hope I am a bit clearer.