Funciton & VARCHAR2 problem

if i hard code the variable i get the right result but if the parameter is passed in as a VARCHAR2 it doesn't work. what is wrong?

   FUNCTION dCount (p_code IN VARCHAR2)
   RETURN NUMBER IS
        result NUMBER;
   BEGIN

	select count(*) INTO result from dd a
	where a.code=p_code	-- works fine if i say a.code='HR';
      RETURN result;