Creating dependent dropdown lists and autofilling

Hello!

I'm building a supplier list for my firm and want to connect it to an index system that relates to a physical library of brochures and samples and such.
I have an index system that uses columns for Heading, Sub-heading and Index code. The task is to create dependent lists as well as auto-filling once a selection has been made.

The final outcome I'm hoping for is:
1. Once a Heading item and Sub Heading item have been selected, the Index code is automatically filled in.
2. Once an Index Code has been selected, the Heading and Sub Heading items auto fills in.

Sheet 1 has the suppliers and sheet 2 has the index.


If anyone can point me to a tutorial, previous discussion or offer any of their own wisdom, I'll be most appreciative.

Thanks, Will


OS: Windows 10
Version: 2209