一般來說，關機或Logff后，Windows會傳依序送出WM_QUERYENDSESSION的信息給每個Process，如果中間有一個Process不能順利結束(例如：Word修改后未存檔，而出現是否存檔，但我們按取消)，這時該信息執行的結果會傳回False(0)，這時Windows也就不再繼續送WM_QUERYENDSESSION給下一個Proccess。反之，如果所有的Process都可以順利結束(也就是每個送出的WM_QUERYENDSESSION都傳回True)，那才代表以以順利結束。

不管WM_QUERYENDSESSION最后的結果是可以順利結束或不能順利結束，Windows會再送一個WM_ENDSESSION的信息給所有的Process，而wParam的內容便是指出是否可以順利結束(True菜單可以，False菜單不行，在vb中則CheckwParam = 0 菜單False ，0菜單True)，說到這里大概就知道該如何做啦，程序如下：

’以下在Form
Private Sub Form_Load()
Dim ret As Long
’記錄原來的Window Procedure的位址
preWinProc = GetWindowLong(Me.hwnd, GWL_WNDPROC)
’設定form的window Procedure到wndproc
ret = SetWindowLong(Me.hwnd, GWL_WNDPROC, AddressOf wndproc)
End Sub

Private Sub Form_Unload(Cancel As Integer)
Dim ret As Long
’取消Message的截取，而使之又只送往原來的Window Procedure
ret = SetWindowLong(Me.hwnd, GWL_WNDPROC, preWinProc)
’這里只是要看看用關機的方式結束程序時，會不會執行到這里
Dim fno As Long
fno = FreeFile
Open "c:t2" For Append As fno
Print #fno, "ccc" + vbCrLf
Close #fno
End Sub

’以下在.Bas

Option Explicit

Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" _
(ByVal hwnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As Long
Declare Function GetWindowLong Lib "user32" Alias "GetWindowLongA" _
(ByVal hwnd As Long, ByVal nIndex As Long) As Long
Declare Function CallWindowProc Lib "user32" Alias "CallWindowProcA" _
ByVal lpPrevWndFunc As Long, ByVal hwnd As Long, ByVal Msg As Long, _
ByVal wParam As Long, ByVal lParam As Long) As Long

Public Const GWL_WNDPROC = (-4)
Public Const WM_ENDSESSION = &H16
Public Const WM_QUERYENDSESSION = &H11

Public preWinProc As Long

Public Function wndproc(ByVal hwnd As Long, ByVal Msg As Long, _
ByVal wParam As Long, ByVal lParam As Long) As Long
If Msg = WM_QUERYENDSESSION Then
Debug.Print "QryEnd", wParam, lParam
Else
If Msg = WM_ENDSESSION Then
If wParam 0 Then ’代表將順利關機或LogOff，這時便得做正常結束程序的操作
Dim fno As Long
Open "c:tt" For Output As #1
Print #1, "hahcccc5"
Close #1
End If
End If
End If
’將之送往原來的Window Procedure
wndproc = CallWindowProc(preWinProc, hwnd, Msg, wParam, lParam)
End Function