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a new client will adapt to the exercise so fast that by the next time you perform the exercise, their 1 rep max may be out of date and thus their percentages would be incorrect (if they used to bench 100lbs, but after 2 workouts they can bench 110lbs, that 60% you have them working out as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).
This may sound a little unfair. After all, a standard Microsoft installation would include something called Equation Editor. Suffice to say, it wasn‘t advertised in the promotional videos. Software like Matlab was considered vastly superior and had the added advantage that you could analyze the equations as well. Anyway, the good news is that Microsoft has taken a big step forwards with Office 2010 and it‘s now possible to correctly display formulas in a pretty painless fashion. In Excel 2010, you should select the Insert ribbon, and click Equation. This creates a textbox and brings up a whole new ribbon with options for inserting equations. As well as providing easy access to the main Greek symbols, Microsoft have provided quick access to a number of simple functions, such as fractions and exponentials.