I was inspired by the Parabola Calculator version 2.0 to write my own parabola calculator, not in VB (It sucks to start VMWare / Wine / etc. just to run the calculator) ;-)  It doesn't have all the functionality as the Parabola Calculator v2.0 but it is a good start.  It is web based, simple JavaScript.  You can  use it here. (No guarantees on its accuracy)