C#

WindowsEnumerator enumerator = new WindowsEnumerator();
          
foreach (WindowsEnumerator.ApiWindow top in enumerator.GetTopLevelWindows())
{
    if (top.MainWindowTitle == "Client Builder")
    {
        foreach (WindowsEnumerator.ApiWindow child in enumerator.GetChildWindows(top.hWnd))
        {
            if (child.ClassName == "Child_ClassName" && child.MainWindowTitle == "Child_Title")
            {
                IntPtr Chd_win = IntPtr.Zero;

                // GUI 
                Chd_win = FindWindowEx(hwnd, Chd_win, child.ClassName, child.MainWindowTitle);
                           
                PostMessage(Chd_win, WM_LBUTTONDOWN, 5, 5); // button down 
                PostMessage(Chd_win, WM_LBUTTONUP, 5, 5); // button up
                           
                MessageBox.Show(child.ClassName + ", " + child.MainWindowTitle, "");
            }
        }
    }
}