The payment function PMT in Microsoft Excel, used for the calculation of mortgage payments, written as a Javascript application. I have packaged the calculator using Adobe Air. Adobe Air is a Cross-operating system runtime that lets developers combine HTML, AJAX, Adobe Flash, and Flex technologies to deploy rich Internet applications on the desktop. Companies like eBay, AOL, and NASDAQ are already using Adobe AIR to deliver engaging RIAs to their users' desktops. To run the application, you will need to first download and install Adobe Air on your computer. Then click on the Download Adobe Air PMT link above.