stored procedure / Function

Hi,

How to retrieve the IN parameter of a function for later use ?

i tried this :

CREATE OR REPLACE FUNCTION "public"."SP_U_001" ("TypeOfArticle" varchar) RETURNS SETOF "public"."active_articles" AS
$body$
DECLARE
  TypeArt VARCHAR := TypeOfArticle;
    rec RECORD;
    res active_articles;
/**************************************/
BEGIN

  SELECT articletypes.articletype_id INTO tpart FROM articletypes   
    WHERE articletypes.articletype_type = TypeArt;
....

but it seems that      TypeArt VARCHAR := TypeOfArticle;     does not work....

Can you help me ?
thx.
AL.