How to make Job Family and Job Function fields read only when a position based req is created

Summary: Business requirement is the Job Family and Job Function fields are expected to be read only so the defaulted values are not changed/updated when a Position based req is created. Looking for guidance to achieve this.

Content (please ensure you mask any confidential information): We are working on a requirement to make Job Family and Job Function fields read only from Requisition Structure section. But the fields are required to be read only when a Position based requisition is created. For all other types(Template, Existing Requisition) the fields has to be editable. Can anyone guide with the EL expression to add in Page Composer as it already has seeded expression and how to tweak it with our requirement?