ESS Travel / Trip Create Enhancement method

Question

Hi , I am new to HR - Travel Management,
Requirement :
During Create Trip Request from ESS (Tcode - TRIP at backend) a check is required to be added to see if 2 settlements are pending to be approved then create trip shouldnt let user save the new trip and error meesage needs to be displayed about this check.as only maximum of 2 trips could remain unsettled.
Query : As the user will only use ESS , I went through Class - CL_FITE_ASSISTANCE and CL_FITE_EES_ASSISTANCE but couldnt get idea if any of its method a needs to be enhanced or what could be the starting point to begin with its solution.
any kind of help or atleast a direction to be taken will be appriciated.

Answer 1

The Thread can now be closed .
For this the approach used was :
As Trip could be raised in SAP GUI as well as Portal.
So code needs to me made at both places :
BADI and Exit
BADI : TRIP_WEB_CHECK also for Error message fill the error message in message handler.
  DATA exit_message_handler TYPE REF TO cl_hrpa_message_list.
    DATA message_handler TYPE REF TO if_hrpa_message_handler.
    DATA msg TYPE symsg.
    DATA is_ok TYPE boole_d.
    CREATE OBJECT exit_message_handler.
    message_handler = exit_message_handler.
    msg-msgid = 'ZFI'.
    msg-msgty = 'E'.
    msg-msgno = '003'.
    msg-msgv1 = 'Please Settle your Earlier Trips Before'.
    CALL METHOD message_handler->add_message
      EXPORTING
        message = msg
        cause   = message_handler->unknown.
    is_ok = space.
  exit_message_handler->add_messages( message_handler ).
This will show error message on the portal itself and control will not go to the exit.
For EXIT use :
Enhancement : FITR0005   - > Exit : EXIT_SAPMP56T_003.
Method : PTRA_UTIL_TRIPS_GET_LIST to get Employee Trip Details And did the calculations as required. display the Error message if the conditions are not met.