Question: How to set up duplicate check on a custom field?

Question: How to set up duplicate check on a custom field?

Hello All,

I have been working with CRM for some time now and I must admit I have not figured out how to set up a check on a custom field.

Our Company uses a Danish service with Market Data to search for "leads" Each Company in denmark has a Unique ID which i would like to be able to search for or create a rule on. Just like the "rule" that you cannot have 2 leads with the same email.

What I have done so far is just create the "field" and when i do my import I have inserted the "Unique ID" in that field.

Can anyone give me some pointers on how to proceed?