1. close all office applications.
2. open Control Panel ----> Clock, Language, and Region category.
3. click Region then additional settings ---> Currency tab
4. Paste your bitcoin Currency symbol on Currency symbol *
5. click ok, then apply and ok.
6. open excel then use same way for adding $.
* you can get bitcoin symbol from "0234 alt+x".
This is a screen from my PC ----> https://i.imgur.com/635Rk6q.png