How to Track hours on equipment

Hello all,

I am trying to track hours on equipment in my base and seem be having an issue getting the result I would like due to my lack of knowledge in formulas. I am going to break this down into sections.

Where I get my data,
I have integrated my Jotform with my base for inspection sheets on heavy equipment and have it assigned to fill a table called Inspections. everything in this section works perfect and i collect all the data from the forms.

What I am trying to do.
One of the columns I am trying to track is the Engine hours column which is located in the Inspection table. each piece of equipment in the inspection table can have multiple inspections a day. I am trying to track it in another table called Equipment Log which each piece of equipment is automated to link to its inspection record. I have tried using Rollup to Sum the total Engine Hours the unit has been inspected to have. the problem I am facing is the inspector only has to put the hours that are displayed on the machine Example: 2353.8. the problem i am facing is if another inspection comes in and the hours read 2453.0 I end up with ( 2,353.8 + 2,453.0 = 4,806.8) where I really only need to know the Difference between from the first inspection record and every inspection after that. So I can track due dates for oil changes and regular maintenance.

My end goal is to have the equipment hours automatically tracked and to send out an email once the equipment has reach X amount of hours so we know its time for service.

any input would be greatly appreciated.

Hey, unless you’re familiar with scripting, the only way to do this (as far as I know) is to link every record to a rollup so that you can get the oldest / newest records via formula fields, and then find the difference from there

I’ve set up a working copy here