Problems defining thresholds using if statements

Dear Community,

I am currently designing a soundscape for an exhibition. Everything is controlled by the live data a the tidal cycle. According to the data I tried to use if statements to go from one phase into the next one. Unfortunately the way I tried it so far didn't work. My first try was to define frames so in case the wave is higher or the same as 0.5 meter and lower than 1m then trigger an event. Unfortunately with each step in the data I receive a trigger instead of only a trigger at each threshold point. Therefore I tried to use simple if statements such as if the value is 1. then trigger. But in that case I only can do it one way but the cycle goes back again and then I am running in issues. Another idea I had was to use two if statements and compare the current data with the previous one, I think this could be a great alternative but I couldn't really figure out how to get the previous value. Tried to look into coll and zl objects, but couldn't really get my head around. Does someone of you maybe have a simple idea, or suggestion where to look? That would be fantastic. THX