Reply To: Making an index in InDesign – some questions, need help!

Oleh Melnyk has a javascript called “detect digit range.jsx” which I believe will do what you are looking for.

This script detect and set digit ranges:
– searches for “1, 3, 5, 6, 8, 10, 11, 12, 15, 16, 18, 19, 20” and turn it to “1, 3, 5, 6, 8, 10-12, 15, 16, 18-20”

I don’t know where I came by it. A Google search turns up a few social media sites that I believe you can contact him from. I have his email address but I don’t have his permission to give it out. Give social media a try first.