Ask HN: How to add INR/custom currency formats in MS Excel

I frequently need to deal with spreadsheets having numbers in the Indian currency (INR).

I have a custom number formatting pattern saved in my notepad that I apply manually when I need it.

> [>=10000000]"Rs. "##\,##\,##\,##0;[>=100000]"Rs. " ##\,##\,##0;"Rs. "##,##0

This is tedious though. (and the above doesn't handle negative values. and it does not align the currency symbol to the left margin of the cell either.)

Without changing the Operating System locale/regional settings, where I may need to tamper with the timezone, currency, date format, and currency/comma formatting across all applications and the entire OS ...

All I want is an ability to apply the INR formatting quickly -- as easily as applying Dollar, Pound, or Yen symbols or selecting short/long date formats.

Desired format:

Rs. -12,34,56,789.42 (negative Twelve Crores Thirty-Four Lakhs Fifty-Six Thousand Seven Hundred Eighty-Nine Rupees and Forty-Two Paise)

At this point I am surprised Microsoft does not build this as a ready-to-use format into its products. Or I am missing something. Any help appreciated.