How to construct a formula to calculate time from one record to the next

What are the chances those 'logs' have any unique identifier AND they are somewhat sequential in their uniqueness?

If so that would be amazing, and somewhat simple to implement.

If not, you would need some type of script to that will sort and write the previous stop values in.

A skilled programmer could do it in about 2-3 hours

Native option: If you want to make a mess of summary fields and lookup fields... You could make stacking summary/lookup fields (my worst nightmare).

Stop 1,  (minimum stop time for the Route)
>then send as a look up
Route - Stop 1,
>Then Stack
Stop 2 (minimum stop that is greater than "Route - Stop 1"
> Then send as a lookup
>Repeat for x number of possible stops.

Thats just the beginning:

Now you need to calculate the previous stop on the same record.
It would be a huge mess of conditional evaluations.... 
if stop 2, then use stop 1 to stop 2, 
if stop 3, then use stop 2 to stop 3,
x repeats.

Unfortunately they don't have completely unique identifiers from one individual record to another. I think the script to sort stops by driver/vehicle and then write the values sequentially, low->high, based on "time of stop" is a great idea. You're right, the second option seems like a nightmare!

Let me know if you want to get a more in depth look.  Or you can have one of your guys take a crack at it.

mneil@mcftech.com