How to Default value in DFF via SQL option which is dependent on another segment of the same DFF

Summary:

There is a requirement to auto-populate a field with a default value which is dependent on another DFF segment value.

select substr(pf.display_name,1,150)

from PER_ALL_PEOPLE_F PA,per_person_names_f PF,HR_ALL_ORGANIZATION_UNITS_F HR,PER_DEPARTMENTS PD

where PF.PERSON_ID = PA.PERSON_ID

AND PD.ORGANIZATION_ID = HR.ORGANIZATION_ID 

AND PA.PERSON_NUMBER = HR.ATTRIBUTE4

and pf.name_type = 'IT'

and hr.attribute6 = :{SEGMENT.XXSOG_COST_CENTER}

and hr.effective_end_date > sysdate

and pd.effective_end_date > sysdate

XXSOG_COST_CENTER is the other segment of PO_LINES DFF from which I would auto-populate the second one segment.