Unique field for integration

Hi all,

I want to create an interface from C4C to external ERP system.

in the ERP system, address name is a primary key. since this is not the situation in C4C, I want to create a new field "ERP Address ID" which will have a unique id for this address in a specfic account.

Is there any way to make a field unique? (=won't allow duplicates value)

Thanks,

Dror