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Пример из API-Guide

Private Const FILE_NOTIFY_CHANGE_ATTRIBUTES = &H4
Private Const FILE_NOTIFY_CHANGE_DIR_NAME = &H2
Private Const FILE_NOTIFY_CHANGE_FILE_NAME = &H1
Private Const FILE_NOTIFY_CHANGE_SIZE = &H8
Private Const FILE_NOTIFY_CHANGE_LAST_WRITE = &H10
Private Const FILE_NOTIFY_CHANGE_SECURITY = &H100
Private Const FILE_NOTIFY_CHANGE_ALL = &H4 Or &H2 Or &H1 Or &H8 Or &H10 Or &H100
Private Declare Function FindFirstChangeNotification Lib "kernel32" Alias "FindFirstChangeNotificationA" (ByVal lpPathName As String, ByVal bWatchSubtree As Long, ByVal dwNotifyFilter As Long) As Long
Private Declare Function FindCloseChangeNotification Lib "kernel32" (ByVal hChangeHandle As Long) As Long
Private Declare Function FindNextChangeNotification Lib "kernel32" (ByVal hChangeHandle As Long) As Long
Private Declare Function WaitForSingleObject Lib "kernel32" (ByVal hHandle As Long, ByVal dwMilliseconds As Long) As Long
Private Declare Function ResetEvent Lib "kernel32" (ByVal hEvent As Long) As Long

Private Sub Form_Load()
    Dim Ret As Long
    'Set the notification hook
    Ret = FindFirstChangeNotification("C:\", &HFFFFFFFF, FILE_NOTIFY_CHANGE_ALL)
    'Wait until the event is triggered
    WaitForSingleObject Ret, &HFFFFFFFF
    MsgBox "Event Triggered for the first time"
    'Reactivate our hook
    FindNextChangeNotification Ret
    'Wait until the event is triggered
    WaitForSingleObject Ret, &HFFFFFFFF
    MsgBox "Event Triggered for the second time"
    'Remove our hook
    FindCloseChangeNotification Ret
End Sub