I'm assuming that the algorithm for performing the calculation is in the
public domain...?

If so, then this looks a fairly trivial exercise:

1) Ask the user to fill in some boxes

2) Do the calculation

3) Display the results in a grid

Note the parameters that are being asked for: three rules and two actual
numerical values expressed as monetary units. The rules in this context are
dependencies mandated by regulators. Hence, the rules can be learned from
the state(s) and or counties your client wants to do business in -- or --  
tell them they can hire a smart guy who is not lazy and let them know you
have somebody in mind... :-)

<%= Clinton Gallagher
        NET csgallagher AT metromilwaukee.com
        URL http://clintongallagher.metromilwaukee.com/