Well, let‘s take a look at your situation. What level are your athletes or clients at? New athletes or clients probably would not benefit from percentages as much as more advanced clients, as they need to learn how to perform the lift correctly first and foremost. Second, a new client will adapt to the exercise so fast that by the next time you perform the exercise, their 1 rep max may be out of date and thus their percentages would be incorrect (if they used to bench 100lbs, but after 2 workouts they can bench 110lbs, that 60% you have them working out as now too low to cause the adaptation you are looking for).
Thirdly, you can start use a spreadsheet program to schedule your time or organise all kinds of stuffs. You can use it to un-clutter you life by having different checklist on spreadsheets. After you learn the basics of spreadsheet programs, you can come up with more creative ways to use it in your daily life. You can even use a spreadsheet program to assist your weight loss plan. Use it to record your daily food intakes and you weight.