Como criar dinamicamente uma variável com o tipo de dados da tabela?

DECLARE  
  v_stmt_str       VARCHAR2(200);
  v_cur            INTEGER;
  v_rows_processed INTEGER;

  col_cnt     INTEGER;
  rec_tab     DBMS_SQL.DESC_TAB;
  rec         DBMS_SQL.DESC_REC;

  num_var NUMBER;
  string_var VARCHAR2(4000);
  date_var DATE;
  -- .. some more variables if needed 
BEGIN
  v_cur := DBMS_SQL.OPEN_CURSOR; -- open cursor 
  v_stmt_str := 'SELECT whatever from ....';
  DBMS_SQL.PARSE(v_cur, v_stmt_str, DBMS_SQL.NATIVE); 
  DBMS_SQL.DESCRIBE_COLUMNS(v_cur, col_cnt, rec_tab);  

  FOR c in 1..col_cnt LOOP
     rec := rec_tab(c);
     IF rec.col_type = DBMS_TYPES.TYPECODE_NUMBER THEN
         DBMS_SQL.DEFINE_COLUMN(v_cur, c, num_var); 
     ELSIF rec.col_type = DBMS_TYPES.TYPECODE_VARCHAR2 THEN
         DBMS_SQL.DEFINE_COLUMN(v_cur, c, string_var, rec.col_max_len); 
     ELSIF rec.col_type = DBMS_TYPES.TYPECODE_DATE THEN
         DBMS_SQL.DEFINE_COLUMN(v_cur, c, date_var); 
     -- .. some more data types if needed
     END IF;
  END LOOP;

  -- Execute
  v_rows_processed := DBMS_SQL.EXECUTE(v_cur);  
  LOOP 
    -- Fetch a row 
    IF DBMS_SQL.FETCH_ROWS(v_cur) > 0 THEN 
      FOR c in 1..col_cnt LOOP
        rec := rec_tab(c);
        IF rec.col_type = DBMS_TYPES.TYPECODE_NUMBER THEN
            DBMS_SQL.COLUMN_VALUE(v_cur, c, num_var); 
        ELSIF rec.col_type = DBMS_TYPES.TYPECODE_VARCHAR2 THEN
            DBMS_SQL.COLUMN_VALUE(v_cur, c, string_var); 
        ELSIF rec.col_type = DBMS_TYPES.TYPECODE_DATE THEN
            DBMS_SQL.COLUMN_VALUE(v_cur, c, date_var); 
        -- .. some more data types if needed
        END IF;
      END LOOP;
      -- Process: do something with num_var or string_var or date_var values
    ELSE
      EXIT; 
    END IF; 
  END LOOP; 
  DBMS_SQL.CLOSE_CURSOR(v_cur); -- close cursor
END;
/