Validation of selection screen can be performed in the AT SELECTION SCREEN event.
Example:
************************************************************************
* AT SELECTION SCREEN *
************************************************************************
at selection-screen.
perform validate_selection_screen using g_returkode.
if g_returkode = c_returkode_error.
exit.
endif.
*&---------------------------------------------------------------------*
*& Form validate_selection_screen
*&---------------------------------------------------------------------*
* Validation of selection screen
*----------------------------------------------------------------------*
* -->P_G_RETURKODE text
*----------------------------------------------------------------------*
form validate_selection_screen using p_returkode.
if s_framd > 12 or s_framd < 1 or s_tilmd > 12 or s_tilmd < 1.
message e998.
p_returkode = c_returkode_error.
exit.
endif.
if s_framd > s_tilmd.
message e997.
p_returkode = c_returkode_error.
exit.
endif.
if s_fraaar < s_tilaar.
message e996.
p_returkode = c_returkode_error.
exit.
endif.
ENDFORM.