Difference between field values in different records
I am new to filemaker so bear with me. I have gone through all of the functions and many webpages and haven't come up with a solution.
I have a table of meter readings with credit remaining on the meter and I need to subtract the previous meter reading from the current meter reading to know how much credit was used in a period. I have a table of 22,000 meter readings and need to know how much credit was used since the previous readings.
It seems like there must be some kind of self reference solution for this.
Additionally, I will need to exclude answers where the difference is negative or more than 2, but I can figure that out with an If statement.
Thanks for your help.
|Meter ID||Time stamp||Balance||Credit used|
|M0001||time1||5||some calculation goes here|