Adding "last update date" field to list view and auto-updating based on another field

Our team is using Asana to drive weekly team meetings and we simply want to have the list view of tasks with a few relevant fields, including custom fields “Latest Update” and “Latest Update Date”. I want the “Latest Update Date” to be populated automatically when the “Latest Update” field is changed. No other changes on the task should trigger this. I’m happy to script this via the API, but looking for help and ideas on how best to go about this.s

A sandbox view of the list view is attached.