Form Validation

[whitelexi]

I have a form with which my colleagues and i enter data into a table. I would like to make sure that the same data is not entered twice by 2 or more different people, so i want to attach a validation code that would check that the reference number has not been entered into that table in the past, before accepting the data.

Can anyone pls refresh my memory on what code i need to achieve this?

 

[whitelexi]

Please can someone tell me the format for the DLookup validation, if my table name is "Analysts" and the field i'd like to look-up is called "AnalystID". When entering this AnalystID data into the form, how do i write the code in the code builder and also be confident that it will work.