NetSuite Workflow - Set Field Mandatory Option

I am creating a NetSuite workflow to set a field mandatory. Use case as follows:

If custom field "Customer Has Billing Issue" checkbox is checked, then make "Billing Issue Ticket Number" (custom field) mandatory.

Settings as follows: Workflow: Name: (any) Record Type: Customer Sub Types: Customer Execute as admin: checked Status: Released (in Sandbox) Event definition: On create, on view or update Trigger type (I've tried all): Current set to Before Record Load

State: Action 1: Set field Mandatory: Condition: Company has billing issue = T Trigger on (I've tried them all) currently on: After field edit Triggering Client fields: Customer has billing issue Parameters: Field: Billing Issue Ticket Number Mandatory = Checked

Action 2: Set field Mandatory: Condition: Company has billing issue = F Trigger on (I've tried them all) currently on: After field edit Triggering Client fields: Customer has billing issue Parameters: Field: Billing Issue Ticket Number Mandatory = Unchecked

I tried all combinations. The workflow is triggering but I cant seem to make the field mandatory. Any suggestions?