Custamization oracle apps forms using Code based method(ZOOM)

1)Open CUSTOM.pll go to the function called zoom_available
 and write the following code in the palce of "Real Code Starts Here"

    form_name  varchar2(30) := name_in('system.current_form');
    block_name varchar2(30) := name_in('system.cursor_block');
  begin
    if (form_name = 'POXRQERQ' and block_name = 'PO_REQ_HDR') then
      return TRUE;
    else
      return FALSE;
    end if;
2)Goto the Event Procedure and write the follwing code in the place of "Real Code Starts here"
   
form_name      varchar2(30) := name_in('system.current_form');
    block_name     varchar2(30) := name_in('system.cursor_block');
    begin
 
     if (event_name = 'ZOOM')  then
      if (form_name = 'POXRQERQ' and block_name = 'PO_REQ_HDR') then      
        fnd_function.execute(function_name =>   'PO_POXRQVRQ',
        open_flag     =>   'Y');
      end if;
     end if;
3)Save the CUSTOM.pll and compile this Execute the CUSTOM.pll
4)Copy both .pll and .plx into the Resource folder
(close the Application before copying into the Application).