Enter the level on A1 for the second tab to produce results. I used the formula from http://wiki.guildwars2.com/wiki/Precision ((0.0025 × Level2) + (0.05 × Level) + 1) to create the spreadsheet.
https://docs.google.com/spreadsheet/ccc?key=0Ah8ZynZXeVjmdE9EaW5uWjg4WGx0bGZEVklyMkpkQWc#gid=0