Dennis is the author of Teach Yourself Microsoft Excel 2000 and a co-author of four other books on spreadsheet software. He has developed customized Excel courses for specific clients, and has recorded over 50 different training courses on Excel topics for Keystone Learning Systems and Lynda.com. Since 2006 he has presented hundreds of public webinars on a variety of Excel topics.
A former employee of Levi Strauss, the University of Colorado, Amoco Oil, and the federal government, Dennis has taught over 5,000 seminars and classes. He has also led numerous training sessions with Apple, IBM, Lexmark, Texaco, Raytheon, Northrop-Grumman and various federal and state agencies.