This should help :)
/********** Option 1 ************/
DEFINE VARIABLE cList AS CHARACTER NO-UNDO INIT "a,b,c,d,a,b,c,d".
DEFINE TEMP-TABLE ttUnique
FIELDS Listitem AS CHAR.
FUNCTION getUniqueList RETURN CHAR (INPUT cList AS CHAR) FORWARD.
MESSAGE "Option 1 : " SKIP...