Framework & WinAPI. случаи "неподчинения"

Public Class Form1
    Public Structure POINTAPI
        Dim x As Integer
        Dim y As Integer
    End Structure
    Public Structure MSG
        Dim hwnd As Integer
        Dim message As Integer
        Dim wParam As Integer
        Dim lParam As Integer
        Dim time As Integer
        Dim pt As POINTAPI
    End Structure
    Public Declare Function GetMessage Lib "user32" Alias "GetMessageA" (ByVal lpMsg As MSG, ByVal hwnd As Integer, ByVal wMsgFilterMin As Integer, ByVal wMsgFilterMax As Integer) As Integer
    Public Const WM_LBUTTONDBLCLK = &H203
    Public Declare Function WindowFromPoint Lib "user32" Alias "WindowFromPoint" (ByVal xPoint As Integer, ByVal yPoint As Integer) As Integer
    Public Const WM_KILLFOCUS = &H8
    Public Const WM_LBUTTONDOWN = &H201
    Private Sub Form1_Shown(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Shown
        Dim prg As Integer
        prg = 1
        Do While prg = 1
            Dim m As New MSG
            Dim wHand As New Integer
            wHand = WindowFromPoint(Form.MousePosition.X, Form.MousePosition.Y)
            GetMessage(m, wHand, WM_KILLFOCUS, WM_LBUTTONDOWN)
            If m.message = WM_LBUTTONDBLCLK Then MsgBox("OK")
            Application.DoEvents()
        Loop
    End Sub
End Class