Imports System.Windows.Forms
Imports System.Runtime.InteropServices

Public Class CustomForm
    Inherits Form
    ‘ P/Invoke constants
    Private Const WM_SYSCOMMAND As Integer = &H112
    Private Const MF_STRING As Integer = &H0
    Private Const MF_SEPARATOR As Integer = &H800

    ‘ P/Invoke declarations
    <DllImport("user32.dll", CharSet:=CharSet.Auto, SetLastError:=True)>
    Private Shared Function GetSystemMenu(hWnd As IntPtr, bRevert As Boolean) As IntPtr
    End Function

    <DllImport("user32.dll", CharSet:=CharSet.Auto, SetLastError:=True)>
    Private Shared Function AppendMenu(hMenu As IntPtr, uFlags As Integer, uIDNewItem As Integer, lpNewItem As String) As Boolean
    End Function

    <DllImport("user32.dll", CharSet:=CharSet.Auto, SetLastError:=True)>
    Private Shared Function InsertMenu(hMenu As IntPtr, uPosition As Integer, uFlags As Integer, uIDNewItem As Integer, lpNewItem As String) As Boolean
    End Function


    ‘ ID for the About item on the system menu
    Private SYSMENU_ABOUT_ID As Integer = &H1

    Public Sub New()
    End Sub

    Protected Overrides Sub OnHandleCreated(e As EventArgs)
        MyBase.OnHandleCreated(e)

        ‘ Get a handle to a copy of this form‘s system (window) menu
        Dim hSysMenu As IntPtr = GetSystemMenu(Me.Handle, False)

        ‘ Add a separator
        AppendMenu(hSysMenu, MF_SEPARATOR, 0, String.Empty)

        ‘ Add the About menu item
        AppendMenu(hSysMenu, MF_STRING, SYSMENU_ABOUT_ID, "&About…")
    End Sub

    Protected Overrides Sub WndProc(ByRef m As Message)
        MyBase.WndProc(m)

        ‘ Test if the About item was selected from the system menu
        If m.Msg = WM_SYSCOMMAND AndAlso m.WParam.ToInt32 = SYSMENU_ABOUT_ID Then
            MessageBox.Show("Custom About Dialog")
        End If
    End Sub
End Class