Auto assign a unique reference number to every new field

Hello,

I need to created a new database effectively.  So lets say I create a new separate entity, then upload a list of 100 companies into that entity.

What I need is for each of them to be assigned a reference ID.

I though about simply using the GUID that the CRM assigns it, but I cannot pull that from a field within the CRM, can i?

If not, is it possible to start a new entity from scratch, and assign each new record a reference number of it own, that I can then directly report on?

Many thanks
David