调用sendMessageA老出错为何?该如何解决

调用sendMessageA老出错为何?
声明:
Function long FindWindowA(String lpClassName,String lpWindowName) Library "user32.dll"
Function long sendMessageA(Long hwnd,long wmsg,long lparm,long sparm) Library "user32.dll"

调用:

hnd=FindWindowA(ls_tmp,ls_title)

if hnd>0 then
sendMessageA(hnd,16,0,0)
end if

错误信息:
Bad runtime function reference at line 16 in close event of object w_main.


------解决方案--------------------
SendMessageA
"S"应该大写