Dennis @ PerfectForms
This capability is certainly not native in PerfectForms,. You could probably build the behavior. The first step is to fully and completely define the requirement. Once you have done that you may find that there is a web service available to do the calculation for you. Then you would simply have to create a web service connection as described in our help guide: /Documentation/manual/html/?d_webservicesconnections.htm. If you need it built in PerfectForms we could provide a quote once the requirements are fully defined.