No formula can alter values without user interaction. so, even if you wrote a formula that checked for zero values, once the value has been set, it will not be altered without a push of the button, or some other command entered in by the user.
Why not use a database with an entry form? Then you just write reports against the entered data, and no programming is really needed. If the user sees bogus info on the report, they delete the entry or correct the entry in the table.