begin块内部是否可以定义游标？

yangjavine

CREATE OR REPLACE FUNCTION get_localcost(msisdn VARCHAR2) RETURN NUMBER
IS
  v_Intercost NUMBER;
  v_chargetime VARCHAR2(24);
  t_chargetime VARCHAR2(24);
  sumIntercost NUMBER;
  tempcount NUMBER;
  No_result EXCEPTION;
  BQ_201111_MSISDN VARCHAR2(800);
  bq_sql VARCHAR2(800);
  BQ_TAB_MSISDN VARCHAR2(24);
  result_sql VARCHAR2(800);
  localcost NUMBER;

BEGIN
  BQ_TAB_MSISDN:=BQ_TAB_||substr(msisdn,length(msisdn)-2,3);
  bq_sql:='declare bq_cusor cursor for select S_16_STTIM,I_COST From '||BQ_TAB_MSISDN||' Where S_24_MSISDN='||msisdn||' And S_4_2=3 Order By S_16_STTIM asc;';
  open bq_cusor
  loop
    fetch bq_cusor into BQ_201111_MSISDN
    exit when bq_cusor%notfound;
    v_chargetime:=bq_cusor.S_16_STTIM;
    v_Intercost:=bq_cusor.I_COST;
    if (sumIntercost>=100000 or tempcount>50) then
                t_chargetime:=v_chargetime
                exit;
    end if;  
    sumIntercost:=sumIntercost+v_Intercost;
  end loop;
  close bq_cusor;
EXCEPTION
  WHEN no_result THEN
    DBMS_OUTPUT.PUT_LINE('caculate wrong');
    result_sql:='Select sum(I_COST) From '||BQ_TAB_MSISDN||' Where S_24_MSISDN='||msisdn||' And S_4_2!=3 And S_16_STTIM>'||t_chargetime||';'
    execute immediate into localcost;
    RETURN localcost;
END;

帮忙看下毛病在哪里？是不是begin块不能定义游标，还是有另外的方式可以在begin块定义游标？
定义游标后，应该怎么执行这个游标，让游标生效？
谢谢