Thanks for the effort but you shouldn't make an heavy application for a calculator, it's not safe.
Or at least make it open source cause a virus scan on a website means nothing.
A web application js/html5 is way more suited for that cause it would be 99.9% secure for us. (it even can be faster to make if you use the right libs => knockoutjs.com - jquery.com - jqueryui.com).