Public ENDSESSION As Boolean

Private 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
   
Private Declare Function SetWindowLong Lib "user32" _
    Alias "SetWindowLongA" _
    (ByVal hWnd As Long, _
    ByVal NIndex As Long, _
    ByVal wNewWord As Long) _
    As Long

Private Declare Function GetWindowLong Lib "user32" _
    Alias "GetWindowLongA" _
    (ByVal hWnd As Long, _
    ByVal NIndex As Long) _
    As Long
   
Private Const GWL_WNDPROC  As Long = (-4)
Private Const WM_QUERYENDSESSION = &H11

Private PrevWindowProc  As Long

Public Function WindowProc(ByVal hWnd As Long, ByVal uMsg As Long, _
                           ByVal wParam As Long, ByVal lParam As Long) As Long
                           
    Select Case uMsg
      Case WM_QUERYENDSESSION
          If wParam <> 0 Then
          Else
            'Msgbox "WM_QUERYENDSESSION message received"
            ENDSESSION = True
          End If
    End Select
    WindowProc = CallWindowProc(PrevWindowProc, hWnd, uMsg, wParam, lParam)
End Function

Public Sub UnsubClass(hWnd As Long)
    If PrevWindowProc <> 0 Then
        Call SetWindowLong(hWnd, GWL_WNDPROC, PrevWindowProc)
        PrevWindowProc = 0
    End If
End Sub

Public Sub SubClass(hWnd As Long)
    ENDSESSION = False
    PrevWindowProc = SetWindowLong(hWnd, GWL_WNDPROC, AddressOf WindowProc)
End Sub

Private Sub Form_Close()
    UnsubClass Application.hWndAccessApp
End Sub

Private Sub Form_Open(Cancel As Integer)
    SubClass Application.hWndAccessApp
End Sub

Private Sub Form_Unload(Cancel As Integer)
    If Not ENDSESSION Then
        If MsgBox("Close Application?", vbYesNo) = vbNo Then
            Cancel = True
        End If
    End If
End Sub