How to create dynamic ON CHANGE statement? Please help!

Question

Hi Experts,
   I have a requirement where my ON CHANGE criteria is dynamic. It is based on wa_charakeyfrmt-value which I am reading from a table. If it is 'DO' then ON CHANGE will have wa_errtabcopy-DO. Else if it is 'LI' then ON CHANGE will have wa_errtabcopy-LI. There will be many cases like this. So instead of writing so many IF/ELSE or SWITCH/CASE conditions is it possible to dynamically create ON CHANGE criteria for the last field. See the example code below:
   IF wa_charakeyfrmt-value = 'DO'. "On DO change
      LOOP AT i_errtabcopy into wa_errtabcopy
           WHERE sold_to = wa_errtab-sold_to.
              ON CHANGE OF wa_errtabcopy-key_value
                        OR wa_errtabcopy-rep_created_date
                        OR wa_errtabcopy-rep_created_time
                        OR wa_errtabcopy-rep_counter
                        OR wa_errtabcopy-DO.
              ENDON.
      ENDLOOP.
   ELSEIF wa_charakeyfrmt-value = 'LI'. "On LI change
      LOOP AT i_errtabcopy into wa_errtabcopy
           WHERE sold_to = wa_errtab-sold_to.
              ON CHANGE OF wa_errtabcopy-key_value
                        OR wa_errtabcopy-rep_created_date
                        OR wa_errtabcopy-rep_created_time
                        OR wa_errtabcopy-rep_counter
                        OR wa_errtabcopy-LI.
              ENDON.
      ENDLOOP.
     |
Thanks
Gopal

Answer 1

DATA: BEGIN OF text,
        word1(4) TYPE c VALUE 'This',
        word2(4) TYPE c VALUE 'is',
        word3(4) TYPE c VALUE 'a',
        word4(4) TYPE c VALUE 'loop',
      END OF text.
DATA: string1(4) TYPE c, string2(4) TYPE c.
DO 4 TIMES VARYING string1 FROM text-word1 NEXT text-word2.
  WRITE string1.
  IF string1 = 'is'.
    string1 = 'was'.
  ENDIF.
ENDDO.
SKIP.
DO 2 TIMES VARYING string1 FROM text-word1 NEXT text-word3
           VARYING string2 FROM text-word2 NEXT text-word4.
  WRITE: string1, string2.
ENDDO.