Restrict a characteristic with interval values containing pattern

Dear Experts,

I have a requirement where I need to restrict values on charatceristics by excluding an interval like between [200-500] and by including only one value like 199. The characteristic should have a variable as well.

Could you please help me with the coding below?

After have unfortunatelly tried to solve this issues with the standard functionalities, i  decided to go for customer user exits.

I need to be able to dynamically restrict them at runtime.

In the first part of my coding, i am trying to exclude all values between the interval [200-500]. And in the second part, i am trying to find out the value 199.

Any input will be welcome.

IF I_STEP = 1.
        DATA: ITAB TYPE STANDARD TABLE OF /BI0/MASTI WITH HEADER LINE,
                   IACT TYPE of E_T_RANGE

          SELECT * FROM /BI0/MASTI INTO TABLE ITAB WHERE MASTI not between [200-500].

          CLEAR: L_S_RANGE.
          L_S_RANGE-SIGN = 'E'.
          L_S_RANGE-OPT = 'CP'.

          LOOP AT ITAB.
            L_S_RANGE-LOW = ITAB-MASTI .
            APPEND L_S_RANGE TO E_T_RANGE.
          ENDLOOP.

          CLEAR L_S_RANGE.

LOOP AT E_T_RANGE into IACT.
            L_S_RANGE-LOW = '199'.
            APPEND L_S_RANGE TO E_T_RANGE.

          ENDLOOP.
        ENDIF.

Thanks

Pat