Filemaker Project Adjustments

I have a quick small filemaker project i am working on and need a few little things done on it. It is a Turf Chemical Database used to find the correct chemical for the job and to work out how much of a chemical is needed. The project has 3 little issues. Firstly is to add a filter when a user selects 2 different fields to filter the records and show them in a Portal with the list of compatible chemicals. Second is when a user selects a chemical in the calculator the dosage required is used to complete another field. Finally is when a check box is not selected then this value is not included in the calulation.