We can initial value of SELECT-OPTIONS in event INITIALIZATION.

Example

TABLES: sflight.
SELECT-OPTIONS: s_carrid FOR sflight-carrid.
INITIALIZATION.
  s_carrid-sign = ’I’.
  s_carrid-option = ’EQ’.
  s_carrid-low = ’AA’.
  APPEND s_carrid.
  s_carrid-low = ’AB’.
  APPEND s_carrid.
  s_carrid-low = ’AC’.
  APPEND s_carrid.

The output is: