Need Help in writing Custom Formatter

Hi,

I am working on custom power bi controls as per our needs. In that I want to write a custom formatter which formats the string with my requirements

eg. if value is null than return "No Data Available" instead of "(Blank)". Also If value is available than format it in Indian currency format e.g. Lakhs,Crores etc.

Also can I use this custom formatter in existing control or do I need to write a whole new control to use this formatter.