Can we have auto increment index for Required column on Sharepoint

Hello,

Just wondering if there is a way to get around the Mandatory column rule on Sharepoint.  I mean a dB can have an index column.  But instead of requiring the user to actually enter something there, can we have it auto increment an index for this mandatory column?
 
Basically, I need to add clients to the Sharepoint Contact List, from which we can select them when entering payments on the Account Receivable List.  To do this, I've added a Calculated column on the Contact List with the following:
=IF(ISBLANK([Last Name]),"",[Last Name])&" "&IF(ISBLANK([First Name]),"",[First Name])&" "&IF(ISBLANK(Company),"",Company)

However, some clients have First Name and Last Name, while others would only have Company name.  So I can't have any of these to be come a Required field.

Thanks.