Hello,

I have created a fuel log form using Jotform and airtable base to record the fuel usage which should match the meter reading at the physical fuel tank. There are 2 types of fuel; Diesel and Gasoline. Both are require to record the following details:

- Diesel Tank = This field shows the remaining fuel in the tank. Physically the fuel tank can holds 500 gallons.
- Diesel Start = This field shows the beginning of fuel reading. The start reading should begin with fuel tank 500 gallons = 0.
- Diesel End = This field require the employee to enter the ending of fuel reading after she/him done pumping the fuel into a vehicle/equipment.
- Diesel Total Gallons = This field shows the total gallons that’s has been pumped. (I already got the solution for this field).

My problem in sample use case is — the first employee record the fuel log as following:

- Diesel Tank =
**500**(Auto calculate/ formula) - Diesel Start = 0 (Auto calculate/ formula)
- Diesel End =
*30.9* - Diesel Total Gallons = 30.9 (Auto calculate/ formula)

Then the second or next employee, the fuel log record should be:

- Diesel Tank =
**469.1**(Auto calculate/ formula) - Diesel Start =
*30.9*(Auto calculate/ formula) - Diesel End = 56.3
- Diesel Total Gallons = 25.4 (Auto calculate/ formula)

And it’s continue until the Diesel/Gasoline Tank = 0, then it’s restart again at 500.

What will be the formula for Diesel Tank and Diesel Start? Thank you so much in advanced for the help.