how to make a running calculation with a specific character found in a field
I'm hoping you can help here. I am trying to make a calculation on a layout. I need to calculate measurements of a specific drop down value that I write in a specific field. The value is called "pool." There are other values called "rapids" and "riffles" etc., but I need to write a calculation that finds running totals of the lengths between the "pools." Is it easier to run a script? If so, how to do I do this? FYI- I have another field that gives unit lengths. Again, I want to calculate the unit lengths between the value "pool".
I hope this is clear enough. Ideas? Thanks!