Need rules to tell me what to update

I've attached a demo document to try and show what I am attempting to do

Information is updated by others into a spreadsheet on google docs and I copy/paste this information into Sheet1

I need something to search Sheet1 and Master CSV file sheets, and display what doesn't have an entry ("" indicates no entry) but has since been updated in the google sheets documentation

There are instructions included in the demo worksheet which should hopefully explain what I am trying to do.

The end formula needs to be able to be used across multiple sheets, I have just included 1 (Sheet1) for demo purposes