限制程序单运行，handle代码不管用

[gaojupeng]

int ihapp
ihapp = handle(this,true)
if ihapp > 0 then
MessageBox("出错提示" &
,"本程序在系统中已经运行，请使用或关闭打开的程序！")
halt
end if
为什么上面的代码不管用？

[jlwei888]

function ulong CreateMutexA (ulong lpMutexAttributes, int bInitialOwner, ref string lpName) library "kernel32.dll"



string ls_mutex_name
if handle(GetApplication (), false) <> 0 then
ls_mutex_name = app_setupini+ char(0)
ll_mutex=createmutexa(0,0,ls_mutex_name)
ll_err=GetLastError()
if ll_err = 183 then
MessageBox ("提示信息","程序已经运行了!")
halt;
end if
end if