Running app: http://s3.amazonaws.com/JohnLuskPublic/web/boxdraw.html
This is just a simple HTML5 doo-dad I created to draw boxes with Dart (dartlang.org). Note that since it's HTML5, it will not work with older versions of Internet Explorer (version 9 or less). Try FireFox or Chrome.
Source code: https://github.com/JohnL4/BoxDraw.