I'm trying to set up a display value that calculates the total level that a tank has been pumped down in a 48hour period of time. The only catch is that this tank naturally rises in level or gets pumped in to, but we are only concerned with how much level has gone out of the tank. I can't really think of an easy way to set up this expression as my skills are fairly limited. I tried doing a TagMax-TagMin expression, but it doesnt capture multiple tank pump downs and a simple TagVal from 48 hours ago to now doesn't work for the same reason.
Any help is greatly appreciated,