How to Restrict Values in Select Single Component

Summary:

We are trying to Restrict the values in the Dropdown whcih has the list of Emno. The Data =is coming from $flow. varaibles.EmpBO1 and the value= $application.variables.EmpnoEmpBO2. We want to Restrict the BO2 Empno with another Field of BO2 called EmpDept. so that the EmpNo does not show up in the List of Values if the EmpDept is null.

Please advise how to achieve this

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