@Shane J 

You can write before insert business rule in which you can query the table and find if any previous company with same name exists.  if the company name previously exits then you can append some text  to the company name so that slightly different company subset name will be entered inside the extended table so that there will be no duplicate company names, it will be easier to find out which subset of companies you have in your extended table.

E.g.  ServiceNow in base table

ServiceNow-1 in extended table