Public Class Form1
 
    Private Declare Function GetWindowText Lib "user32" Alias "GetWindowTextA" ( _
        ByVal hwnd As Long, _
        ByVal lpString As String, _
        ByVal cch As Long _
        ) As Long
 
    Private Declare Function FindWindowEx Lib "user32" Alias "FindWindowExA" ( _
        ByVal hwndParent As Long, _
        ByVal hwndChildAfter As Long, _
        ByVal lpszClass As String, _
        ByVal lpszCaption As String _
        ) As Long
 
    Private Declare Function GetParent Lib "user32" (ByVal hwnd As Long) As Long
 
    Public Declare Function SendMessage Lib "user32" Alias "SendMessageA" ( _
        ByVal hwnd As IntPtr, _
        ByVal uMsg As Int32, _
        ByVal wParam As Int32, _
        ByVal lParam As Int32) As Int32
 
    Private WM_NCDESTROY As Integer = &H82
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles MyBase.Load
 
        Timer1.Interval = 1000
        Timer1.Start()
 
    End Sub
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button1.Click
        MsgBox(1, MsgBoxStyle.Question, "h")
        'MessageBox.Show("s", "d", MessageBoxButtons.YesNo)
    End Sub
 
    Private Sub Timer1_Tick(ByVal sender As Object, ByVal e As _
      System.EventArgs) Handles Timer1.Tick
        Dim dlghWnd As Long
        Dim lpString As String 'owners caption
        Dim lhwnd As Long
        Dim hWndOwner As Long
        While lpString <> "Form1" 'owners caption
            lpString = Space(255)
            dlghWnd = FindWindowEx(0&, lhwnd, "#32770", vbNullString)  'Suchen 
            ' nach Fenster mit MsgBox-Handle
            If dlghWnd = 0 Then Exit Sub
            hWndOwner = GetParent(dlghWnd)  'Handle der Owner-Form bestimmen
            GetWindowText(hWndOwner, lpString, 255&)  'Titel der Owner-Form 
            ' bestimmen
            lpString = Mid(lpString, 1, InStr(lpString, Chr(0)) - 1)  'Titel 
            ' der Owner-Form zurechtschneiden
            lhwnd = dlghWnd
        End While
        dlghWnd = SendMessage(lhwnd, WM_NCDESTROY, 0, 0)  'MsgBox schließen
    End Sub
End Class