I like the feature of this trigger type, simple to configure. This trigger generates an error message when duplicate information (based on the column combination defined) is entered into the system. This then halts the process of the user to save duplicate records. Instead of it being an error message, how can I possibly effect a process in the system where a user is warned instead - not a hard stop (probably a warning message pops) indicating that record he is trying to enter/save into the system already exists? If it's really two legitimate and different records (e.g. two persons have the same name and birthday as Leads), the user is able to successfully save the record. Net, I'm trying to accomplish a Warning process instead of having a hard-stop error.
For this I would write custom JS code in the page that uses the AJAX API to query for any records with matching field values. You can then display a JS popup or something similar to ask the user if they want to continue. This would all be custom JS code. You'd need to know the Rollbase AJAX API.
Hope this helps,
Matt