SAP Program to add input fields in a custom screen and implementing output

Program: 

 REPORT zsm_screen.

DATA: lv_output TYPE char10.

DATA: it_dynpfields TYPE TABLE OF dynpread,
      wa_dynpfields TYPE dynpread.

CALL SCREEN 400.

MODULE user_command_0400 INPUT.

  IF sy-ucomm = 'F_CALC'.

    wa_dynpfields-fieldname = 'LV_ONE'.
    APPEND wa_dynpfields TO it_dynpfields.

    wa_dynpfields-fieldname = 'LV_TWO'.
    APPEND wa_dynpfields TO it_dynpfields.

    wa_dynpfields-fieldname = 'LV_OUTPUT'.
    APPEND wa_dynpfields TO it_dynpfields.


    CALL FUNCTION 'DYNP_VALUES_READ'
      EXPORTING
        dyname               = sy-cprog
        dynumb               = sy-dynnr
*       TRANSLATE_TO_UPPER   = ' '
*       REQUEST              = ' '
*       PERFORM_CONVERSION_EXITS             = ' '
*       PERFORM_INPUT_CONVERSION             = ' '
*       DETERMINE_LOOP_INDEX = ' '
*       START_SEARCH_IN_CURRENT_SCREEN       = ' '
*       START_SEARCH_IN_MAIN_SCREEN          = ' '
*       START_SEARCH_IN_STACKED_SCREEN       = ' '
*       START_SEARCH_ON_SCR_STACKPOS         = ' '
*       SEARCH_OWN_SUBSCREENS_FIRST          = ' '
*       SEARCHPATH_OF_SUBSCREEN_AREAS        = ' '
      TABLES
        dynpfields           = it_dynpfields
      EXCEPTIONS
        invalid_abapworkarea = 1
        invalid_dynprofield  = 2
        invalid_dynproname   = 3
        invalid_dynpronummer = 4
        invalid_request      = 5
        no_fielddescription  = 6
        invalid_parameter    = 7
        undefind_error       = 8
        double_conversion    = 9
        stepl_not_found      = 10
        OTHERS               = 11.
    IF sy-subrc <> 0.
* Implement suitable error handling here
    ENDIF.

    READ TABLE it_dynpfields INTO  DATA(wa_one) WITH KEY fieldname = 'LV_ONE'.
    READ TABLE it_dynpfields INTO  DATA(wa_two) WITH KEY fieldname = 'LV_TWO'.

    lv_output = wa_one-fieldvalue + wa_two-fieldvalue.

  ENDIF.


ENDMODULE.

Output: