Нажать на кнопку в диалоговом окне - Visual Basic .NET

Private Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long
    Private Declare Function PostMessage Lib "user32" Alias "PostMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Long) As Long
    Private Declare Function FindWindowEx Lib "user32" Alias "FindWindowExA" (ByVal hWnd1 As Long, ByVal hWnd2 As Long, ByVal lpsz1 As String, ByVal lpsz2 As String) As Long
 
    Sub нажать_на_кнопку()
 
        Dim hwnd As Long
        hwnd = FindWindow(vbNull, "Удалить файл") 'неправильный hwnd
        hwnd = FindWindowEx(hwnd, 0, "Button", "Н&ет") 'неправильный hwnd
        PostMessage(hwnd, 245, 0&, 0&) 'не работает
        PostMessage(hwnd, 245, 0&, 0&) 'не работает
 
        PostMessage(857560, 245, 0&, 0&) 'не работает даже с правильным  hwnd
        PostMessage(857560, 245, 0&, 0&) 'не работает даже с правильным  hwnd
  End Sub