Restrict New Hire life event for part timers

Summary:

We have a requirement, where in we do not need the 'New Hire' life event to trigger for part timer. We tried using the below formula, attached it to data change under 'Per change causes life event'. However, it does not seem to be working.

Any suggestions to achieve the requirement would be helpful.

Code Snippet (add any code snippets that support your topic, if applicable):

/***********************************************************
DESCRIPTION: FORMULA TO TRIGGER NEW HIRE ONLY FOR FULL TIME EMPLOYEES
***********************************************************/
DEFAULT FOR PER_ASG_FULL_PART_TIME is ' '
l_return = 'N'
IF (PER_ASG_FULL_PART_TIME = 'FULL_TIME') THEN