Drop down for a field in table maintenance generator

Hi All,

I have created a table maintenance for a table.

I need to give F4 help for a field as a drop down, as of now i am using POV event and PAI event to get it triggered and captured.

It is working fine, but as my field is key field, once i select any value from drop down  all other key fields are becoming disable for input.

code in POV event in flow logic is,

SELECT busrule

               FROM z100_pro

               INTO CORRESPONDING FIELDS OF TABLE it_bus.

  CALL FUNCTION 'F4IF_INT_TABLE_VALUE_REQUEST'

    EXPORTING

      retfield        = 'BUSRULE'

      value_org       = 'S'

    TABLES

      value_tab       = it_bus

    EXCEPTIONS

      parameter_error = 1

      no_values_found = 2

      OTHERS          = 3.

code in PAI event is,

  CASE ok_code.

    WHEN 'SELECTED'.

      MESSAGE i888(sabapdocu) WITH z100_sup_shdw-busrule.

  ENDCASE.

Can any one please help me on this.

Thank you,

Regards,

Kusuma K.