Private Sub form1_Load(ByVal sender As System.Object, ByVal e As _
   System.EventArgs) Handles MyBase.Load
        Dim hwnd As Integer = getWindowHandle()
        If hwnd = -1 Then Return
        Try
            SendMessage(hwnd, WM_COPYDATA, 0, 0)
        Finally
        End Try
    End Sub
    Public Declare Function SendMessage Lib "user32" Alias "SendMessageA" ( _
      ByVal hwnd As Int32, ByVal wMsg As Int32, ByVal wParam As Int32, ByVal _
      lParam As Integer) As Int32
    Declare Function FindWindow Lib "user32.dll" Alias "FindWindowA" (ByVal _
    lpClassName As String, ByVal lpWindowName As String) As Int32
    Const WM_COPYDATA As Integer = &H4A
 
    Private Function getWindowHandle() As Integer
        For Each p As Process In System.Diagnostics.Process.GetProcessesByName( _
          Process.GetCurrentProcess.ProcessName)
            If p.Id <> Process.GetCurrentProcess.Id AndAlso _
            p.MainWindowTitle = "Form1" Then
                Return p.MainWindowHandle.ToInt32
            End If
        Next
        Return -1
    End Function
 
    Protected Overrides Sub WndProc(ByRef m As System.Windows.Forms.Message)
        MyBase.WndProc(m)
        Try
            If m.Msg = WM_COPYDATA Then
                MessageBox.Show("Nachricht: ")
            End If
        Finally
        End Try
    End Sub

MfG DreamFlasher

I'm not perfect...yet! (MacGyver)
You know the story: Girl meets boy, girl changes boy's subroutines. (Janeway)
I'll be honest with you. My name's not Kirk. It's Luke Skywalker. (Jack O'Neill)