How to move custom.pll rules to self service

In Oracle EBS HR R12, I have a rule in professional forms custom.pll to set ass_attribute3 to a certain values based on the assignment_status.  It works great.  

What is the best way to do that in Self-Service?

Here is my code from custom.pll.

IF (Form_Name           =  'PERWSHRG' 

       AND Event_Name         ='PRE-UPDATE'

       AND name_in('system.current_block') = 'ASSGT') THEN

        IF (

          SUBSTR(NAME_IN('ASSGT.D_GROUP_NAME'),5,25)          IN ('Employee Regular', 'Employee Summer','Employee Graduate','Employee Undergraduate','Employee Postdoc')

           and  NAME_IN('ASSGT.USER_STATUS')  IN ( 'Terminated - Do Not Process' , 'Terminated - Processes Pending','Unpaid Leave')