Any MS Office program doesn't support degree format per se.

Macropod's solution assumes the numbers the format is applied to are dates (what is not in your case), and handles them accordingly;
All other solutions convert the value to text string -and are only working solutions for you.

You must have 2 columns - one for degree values, another for display. In case degrees are calculated only, you can hide the real degree column. Whenever you need to refer coordinates in some formula, you have to refer to degree column, not to degree display column.