Hi
I have a field called "Membership number".
If a user enters a Membership number that is already in the comprofiler table I want to block their registration (much in the same way that email values cant be registered twice)
Is the possible with CB?
Do i need a special plugin?

I used the CB Query add on
SELECT * FROM `jos_comprofiler` WHERE `cb_membernumber` = '[value]'
Validate on empty result
Works great!