A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
Use File / Options / Proofing / Autocorrect Options.... In the 'Replace' box, type a dash dash dash, and in the 'With" box, hold down the Alt key and type 0150 on your number pad. Then type three dashes when you want an en dash.
If you replace a single dash with an en dash, you will never be able to enter a subtraction formula again, but who needs to subtract in Excel? ;)