PO Workflow - Approval button click

I created workflow function/database function and the below code getting called from the process "FIND APPROVER". I am expecting when we click on the "APPROVE" button then

funcmode should return "APPROVE". The issue is when I click on "APPROVE" button this customized function getting called however funcmode always return "RUN". I am expecting funcmode should return "APPROVE".Based on approve click I would like to implement some conditions in oracle wf

CREATE OR REPLACE PACKAGE BODY "APPS"."XXBG_VACATION_RULE_CHK" AS
  gcv_package_name constant VARCHAR2(30) := 'XXBG_VACATION_RULE_CHK';
  po_error         exception;

  PROCEDURE find_approver(
    itemtype IN VARCHAR2,