This is an Excel Spreadsheet in both 2003 and 2013 (so it works with any version of Excel 2003, and above). It is set up for singles, and duos. It is password protected to avoid accidentally deleting the formulas.
You can have up to 100 people on the singles page, and 10 teams are setup on the duos page. You can copy and paste to create more teams.
Directions are given if you want to modify.
You also receive a list of rules to help you run your weight loss challenge.