递归查找子窗口

HWND  findsubwindow(HWND hwnd,const char* classname,const char* windowname)
{
    HWND thishwnd=0;
    thishwnd= FindWindowEx(hwnd,thishwnd,classname,windowname);
    if(thishwnd)return thishwnd;
    thishwnd = 0;
    while(thishwnd=FindWindowEx(hwnd,thishwnd,0,0)){
        HWND  temphwnd = findsubwindow(thishwnd,classname,windowname);
        if(temphwnd)return temphwnd;
    }
    return 0;
}