Accept only special characters in Selection Screen parameter

Question

I have one input field of type C.

PARAMETERS lv_sep TYPE c.

Field lv_sep should accept only special characters.

Can you help me how i can give this constraint?

Answer 1

you can do checks during AT-SELECTION-SCREEN. You could for instance check the parameter lv_sep for the characters you want to accept.

AT-SELECTION-SCREEN.
if not lv_sep CO '!"§$%&/()=?'.
    message text-e01 type E.
endif.

Answer 2

Because I like to avoid NOT in IF statements when I can, I would propose this:

AT-SELECTION-SCREEN.
IF lv_sep CN '!"§$%&/()=?'.
  MESSAGE text-e01 TYPE E.
ENDIF.