Cumulative total caculation

[I&C Tech]

Application; Excel 97. I am trying to create a spreadsheet to calculate total gallons of throughput in a system. I have actual flow rate (gpm) streaming into a cell in real-time. I am multiplying that cell by another that has elapsed runtime (min) being inputted. The product of this formula is total gallons. (gpm x min = gallons) The problem occurs when the flow rate is reduced to a lesser value. Excel automatically lowers the product to a new lower value of gallons. In reality, the gallons have already flowed and are not reduced. How do I get Excel to calculate the cumulative total of gallons that have flowed over time independent of the present flow rate?

 

[Legacy 98055]

Hi Tech.
How often is your data refreshed? Once per minute? Once per second? Variable? I have created a stock tick simulator and can tweak it a bit to process this data instead. You can have it if you like. Assuming I am understanding you correctly? The GPM are being calculated using elapsed time as part of the equation? Elapsed time being the amount of time from one change of data to the next change and so on...? If so, sounds like a good candidate for using a log file and then manipulating the data on demand in Excel.
Tom