Simple Calculations in Rapidweaver

Does anyone know of a plug-in/stack that would allow one to set up a simple calculator with fields so that a customer accessing the website could enter values and have the result displayed? Basic math calcs only (+, -, *, /)? Could one insert an excel worksheet or a small filemaker app/data file? So far I’ve come up with nothing that would allow a customer to enter simple dimensions and allow a calculation. Anyone have a solution for a non-programmer type??? Thanks!

I bet there’s something on