Approval Groups Dynamic query issue

 Hi Folks,

Our requirement as follow.

If user submitting expense report for "2000" Supervisor approval (Supervisor hierarchy) , then chain of approval hierarchy level by amount required.

While defining chain of authority approvals, I have defined Approval group along with following SQL condition.

SELECT paf.supervisor_id

FROM per_people_x ppx, per_assignments_f paf

WHERE ppx.person_id = paf.person_id

AND paf.supervisor_id is not null

and level = 2

CONNECT BY PRIOR paf.supervisor_id = ppx.person_id

START WITH paf.person_id = (select employee_id from ap_expense_report_headers_all where report_header_id= :transaction_id)

When I am trying to submit expense report for approval, system is displaying following error message