Cheers - I'm a big fan of providing these sort of lightweight applications in conjunction with a research publication. There's a real issue with reproducible research (particularly, though not limited to, the medical field) and this type of thing is a step in the right direction.

Could you provide a link to the code for the algorithm you're implementing? (If I were a better developer, I'd probably be able to find it through your source code, but alas...)

Also, I'd suggest you limit the input fields to numbers within the allowable range. Or, at the very least, to positive numbers.