How to configure list of values in a conditional flexfield using another field as parameter?

A conditional flexfield is configured in the section "requisition details", and based on the context shows up a custom field. I am trying to configure a list of values in this field to return a list of candidates allowed to apply for the selected position in the section "basic info". The conditions and parameters was made using SQL statement in a value set configured in the flexfield attibute as follow:

SELECT ppnf.display_name
     , paam.assignment_id
      , ppnf.person_id
      , hapf.position_code
  FROM per_all_assignments_m                    paam
      , per_person_names_f                       ppnf
      , hr_all_positions_f                       hapf

 WHERE