为何通出不成功？
下面是一个程序的主程序，当按主窗口退出时能正常退出，当在myquit的提问中选“否”时，提示找不到程序myquit.prg

是什么原因？

SET TALK off
SET DELETED on
SET SAFETY off
SET DATE to ansi
SET CENTURY on
SET SYSMENU off
ON SHUTDOWN do myquit //退出系统时调用自定义过程
SET MARK to "- "
_screen.Caption= "µ¥Ïî½±¹ÜÀíϵͳ "
USE bj
IF LEN(ALLTRIM(bjtp)) <> 0
_screen.Picture =bj.bjtp
else
_screen.Picture = "bj.bmp "
ENDIF
USE
DO form pass
OPEN DATABASE main.dbc
PUBLIC jjmc
jjmc=SPACE(10)
set class to myclass
ap=create( "app ")
_screen.Icon = "add.ico "
ap.mainprg
ap.close

PROCEDURE myquit

IF MESSAGEBOX( "你确信要退出本系统吗 ",4+32, "提示 ")=6
CLEAR events
CLOSE ALL
QUIT
ENDIF



[解决办法]
ON SHUTDOWN myquit()