Problem: you need to have a PAI/PBO event after user performs an action on your screen (e.g. clicks a toolbar button).

Solution: to invoke PAI event (and therfore PBO too) you have to emulate a user command in your program.

You can achieve this using below two lines of code.

* invoke PAI/PBO events to refresh the screen status
cl_gui_cfw=>set_new_ok_code( new_code = 'DUMMY' ).
cl_gui_cfw=>flush( ).

DUMMY is to avoid executing any action assigned for the user command, but if you want you can put there a handled user code and this will invoke a desired action.

CASE sy-ucomm.
  WHEN 'DELETE'.
    " do some action - possibly delete something
  WHEN OTHERS.
    " do nothing
ENDCASE.

* invoke PAI/PBO events to refresh the screen status and do nothing
cl_gui_cfw=>set_new_ok_code( new_code = 'DUMMY' ).
cl_gui_cfw=>flush( ).

* invoke PAI/PBO events to refresh the screen status and delete something
cl_gui_cfw=>set_new_ok_code( new_code = 'DELETE' ).
cl_gui_cfw=>flush( ).