How to default role identifier field to "X/Personnumber", X should be dynamic based on assignment?

Summary:

Object: Worker Assignment

Requirement:

When hiring an employee, if Bargaining unit field selected value is "External Teachers" then Default "Role Identifier" field to "X/Personnumber" . X will be 1 for primary assignment and 2 for secondary assignment. X should be dynamic.

Version: 24A

This is a approved use case.

Use Case - 8

Customer Name - East Sussex County Council

Please share the configuration steps, screenshots to match this requirement.

Thanks,

Khadir