Single value calculators for agriculture

I’m an agronomist creating some simple farming calculators and I’ve hit a wall. The calculator I’ve created predicts how many bushels can be grown for several crops just by plugging in how many inches of annual moisture he/she has. The key is all my crops, but I can’t get the option for the moisture value that essentially drives my equation. That single value then produces a lovely bar graph which I have properly setup. I have it on Excel but can’t get it working here. image

Another calculator is where the price of a fertilizer is entered and it gives me the price per pound of nutrient. I think that will be easy enough though. If anyone is interested in doing some freelance teaching by all means I could use some help to speed things up.