I'm looking for a way to determine if the temperature of a zone is rising or falling over a relatively long period of time, say 1 to 2 seconds, using RSLogix 5000 ladder logic. The zone in question uses resistance heat and chilled water for cooling. The idea is to reduce, or stop, chilled water cooling when the process variable above the set point but falling, as a result of the cooling, and increase cooling as the process variable moves above the set point.