Database trigger everytime a user enter a list of things

Hey folks,

i’m having some challenges on how to set my Database trigger.

Situation: i have two data types, User and Workflow. And i want the Database Trigger to perform actions once a User enter a list of users in the Workflow. So the Workflow has a list of users.

I’m trying to do this with (see pic below) but its not working.
image

any advice?