Invariably, I will create and distribute an Excel template only to fall victim to the dreaded formula overwrite offense. It's frustrating when a vacation schedule is returned that doesn't foot, or an item is coded incorrectly in an expense report after significant time has been taken to try and make a template idiot proof. Then some "idiot" spoils the whole thing by hard-coding a number over a formula.
Use the "Protect Sheet" option to help ensure that unwanted changes are not made into your Excel templates.
To illustrate, I have downloaded a template from Microsoft Online. It has a Description in column A, two input columns (Budget in column B and Actual in column C), and two calculated fields (Difference ($) in column D and Difference (%) in column E).
I would like to protect this worksheet so that entries can only be made in the Budget and Actual columns as shown in the highlighted area below.