Change the cs_data and call
CALL METHOD SUPER->IF_FPM_GUIBB_FORM~GET_DATA
EXPORTING
IO_EVENT = IO_EVENT
IV_RAISED_BY_OWN_UI = IV_RAISED_BY_OWN_UI
IT_SELECTED_FIELDS = IT_SELECTED_FIELDS
IV_EDIT_MODE = IV_EDIT_MODE
IO_EXTENDED_CTRL = IO_EXTENDED_CTRL
IMPORTING
ET_MESSAGES = ET_MESSAGES
EV_DATA_CHANGED = EV_DATA_CHANGED
EV_FIELD_USAGE_CHANGED = EV_FIELD_USAGE_CHANGED
EV_ACTION_USAGE_CHANGED = EV_ACTION_USAGE_CHANGED
CHANGING
CS_DATA = CS_DATA
CT_FIELD_USAGE = CT_FIELD_USAGE
CT_ACTION_USAGE = CT_ACTION_USAGE
.