急informix存储过程报错!解决方法

急,informix存储过程报错!
我用informix数据库执行ST_ycheckSheet存储过程，如下:

execute procedure ST_ycheckSheet('H001200902180186','ss');

报错为 语句(1)运行失败：General SQL error.

Variable (__startwork) has undefined value.  

请高手指点一下怎么修改,谢谢!~~


drop procedure ST_ycheckSheet;
create procedure ST_ycheckSheet(sSheetID char(16),sUserCName char(8)) returning Int; 
  define __Err,__BreakPoint,__ISAM int; 
  define __Msg varchar(255); 
  define __StartWork Int; 
   
  define __dutytypeInt; 
  define __flag,__tflag,__c,__iInt; 
  define __mode Int; 
  define __myshopid,__zbshopid,__headid char(4); 
  define __shoptypeInt; 
   
  define __SheetType int; 
   
  ON EXCEPTION SET __Err,__ISAM,__Msg 
  if __StartWork = 1 then 
  rollback work; 
  end if; 
  raise exception -746,0,__Err||','||__ISAM||','||__BreakPoint||'-'||__Msg; 
  END EXCEPTION 
 
  let __BreakPoint = 814600; 
  let __SheetType = 8146; 
 
  begin work; 
  let __StartWork = 1; 
   
  let __BreakPoint = 814605;
  select shopid into __MyShopID from ychecksheet0 where sheetid=sSheetID;
  select shoptype,headid into __shoptype,__headid from shop where id=__myshopid; 
  select id into __zbshopid from shop where id=headid and ifshopgroup=(select ifshopgroup from shop where id=__myshopid);
   
  let __breakpoint=814606; 
  select flag,dutytype into __flag,__dutytype from ycheckSheet0 where sheetid=sSheetID; 
  select count(*) into __c from ychecksheetItem0 a,employee b where a.id=b.id and a.sheetid=sSheetID and b.dutyid in(1009,1010,1013,1014,1137);
  if __flag=0 and __dutytype=0 and __c>0 then
  raise exception -746,0,'选择员工类时不能有管理人员!';
  end if;
  if __flag=0 and __dutytype=0 then 
  let __tflag=100; 
  elif __flag=1 and __dutytype in(1,2) then 
  let __tflag=100; 
  elif __flag=2 then 
  let __tflag=100; 
  else 
  let __tflag=__flag+1; 
  end if; 
  
  if __shoptype=0 and __tflag<>100 then
  let __tflag=__flag+2;
  end if;
   
  let __BreakPoint = 814608; 
  update ycheckSheet0 set (Flag,CheckDate,Checker,PrintCount)=(__tflag,ToDay,sUserCName,0) where SheetID=sSheetID; 
  if dbinfo('sqlca.sqlerrd2')=0 then 
  raise exception -746,0,sSheetID || '单并不存在!'; 
  end if; 
   
  let __BreakPoint = 814610; 
  insert into SheetFlow0(SheetType,SheetID,BeforeFlag,AfterFlag,UserName,Note) 
  values(__SheetType,sSheetID,__flag,__tflag,sUserCName,'审核'); 
   
  let __BreakPoint = 814615; 
  insert into SheetFlow select * from SheetFlow0 where SheetType=__SheetType and SheetID=sSheetID; 
  delete from SheetFlow0 where SheetType=__SheetType and SheetID=sSheetID; 
   
  let __BreakPoint = 814620; 
  if __tflag=100 then
  execute procedure ST_ychecksheet1(sSheetID);
  end if;
  
  commit work; 
  return 0; 
end procedure;

[解决办法]
在ON EXCEPTION之前加一句试试：
let __StartWork = 0;