Execute Immediate with function

CREATE OR REPLACE FUNCTION
single_number_value (
   table_in    IN VARCHAR2,
   column_in   IN VARCHAR2,
   where_in    IN VARCHAR2)
   RETURN NUMBER
IS
   l_return   NUMBER;
BEGIN
   EXECUTE IMMEDIATE
         'SELECT '
      || column_in
      || ' FROM '
      || table_in
      || ' WHERE '
      || where_in
      INTO l_return;
   RETURN l_return;
END;



BEGIN
   DBMS_OUTPUT.put_line (
      single_number_value (
                'employees',
                'salary',
                'employee_id=200'));
END;