ContributionsMost RecentMost LikesSolutionsRe: How to calculate run time from hour meter readingThe State Requires us to log all of the reads and the corresponding run times. We also use the run times for diagnostics. If I understand your explanation, equipment will always know the last read and the previous read (of all the reads). Those values change as subsequent reads are added. I lose the interval run time history. That is why I added snapshots. I wilRe: How to calculate run time from hour meter readingOK Thank you. I will go through it in detail. It will be great to have this working! Re: How to calculate run time from hour meter readingThank you so much for your reply. Your explanation is how I had my table setup prior to moving to the reverse relationship solution. Some issues that I had at the time were that the Added Read (Record) would become the new maximum when saved...resulting in run time = 0. I had to use snapshot fields to preserve the read. It got confusing because the calculation would work prior to saving. The operator could see the run time. When the record was saved the calculation would change (because of the new Max). I had to create conditions to alter the view depending on if it was a new record, edit, view. This is when I changed to the reserve relationship solution. I also had issues with how the mobile app would process the New Record routine compared to the Desktop Version. This was many years ago. The operators are using the mobile app and many of our locations are in areas with poor/no connectivity. I am going to collect the reads with an app that can be used to collect the data. I will need to import the reads into the reads table. The problem is that I won't know the reverse relationship Record ID of the previous read. I can export a list from the equipment table. It will have the [Equipment ID] and Summary Fields [Last Read][Date of Last Read]. The operator can input the current read. I can then Import the data into the Read Table. I will have the equipment ID#, Read Date, Read Value. I won't have the Record ID# to populate the [Related Read Field] (Reverse Relationship) If I could use logic to know what the Record ID# would be maybe there is a solution? Thank you again. How to calculate run time from hour meter readingI own a small utility company and have several operators check in plants. They record the day's meter readings (cumulative hour meters and water meters) in QuickBase. I need to calculate run time based on the previous reading compared to the current reading. I have dozens of facilities, hundreds of meters to read and thousands of reads. Tables: Facilities, Equipment, Reads. The readings are taken on random dates (no defined interval). I have the read table related to itself so that the previous read can be "selected". This has been working but I would like to be able to import a list of reads but I don't know how to populate the record ID required for finding the "previous" read. I think I'm looking for a way to dynamically/logically calculate the key field.