Flow Logic of List Screen 
Flow Logic of List Screen
If you create the single screen for the infotype using transaction PM01 Enhance Infotypes, the system prepares the flow logic.
The flow logic of infotypes within the standard system usually follows this pattern.
Action PBO
PROCESS BEFORE OUTPUT.
MODULE BEFORE_OUTPUT.
MODULE ASSIGN_TC3000.
MODULE VARIATION_TC.
LOOP.
MODULE PSLIST.
MODULE Pnnnn.
ENDLOOP.
MODULE GET_HEADER_SUBSCREEN.
...CALL SUBSCREEN SUBSCREEN_HEADER INCLUDING HEADER_PROG HEADER_DYNNR.
You can carry out infotype-specific initialization procedures within PBO module
Pnnnn . This is the same module that is used for the single screen. If you require different infotype-specific initialization procedures for the list screen, you can determine that a different PBO module is accessed. This module must be called PnnnnL .
You must not change PBO module
Action PAI
PROCESS AFTER INPUT.
MODULE EXIT AT EXIT-COMMAND.
LOOP.
FIELD RP50M-SELEC MODULE MARK ON REQUEST.
ENDLOOP.
CHAIN.
FIELD RP50M-BEGDA.
FIELD RP50M-ENDDA.
FIELD RP50M-SUBTY.
MODULE SELECT_FOR_LIST ON CHAIN-REQUEST.
ENDCHAIN.
FIELD RP50M-PAGEA ON REQUEST MODULE TOP_OF_LIST.
MODULE ADJUST_LIST_TC.
MODULE POST_INPUT_CHECKS.
You must not change PAI modules
EXIT , MARK , SELECT_FOR_LIST and POST_INPUT_CHECKS.