Private Declare Function CreateFile Lib "kernel32.dll" Alias "CreateFileA" _
  (ByVal lpFileName As String, ByVal dwDesiredAccess As Long, _
  ByVal dwShareMode As Long, lpSecurityAttributes As Any, _
  ByVal dwCreationDisposition As Long, ByVal dwFlagsAndAttributes As Long, _
  ByVal hTemplateFile As Long) As Long
 
Private Declare Function LockFileEx Lib "kernel32" _
      (ByVal hFile As Long, ByVal dwFlags As Long,  _
       ByVal dwReserved As Long, _
       ByVal nNumberOfBytesToLockLow As Long, _
       ByVal nNumberOfBytesToLockHigh As Long, lpOverlapped As Any) As Long
 
Private Const GENERIC_READ = &H80000000 ' Nur Lesen
Private Const FILE_SHARE_READ = &H1
Private Const OPEN_EXISTING = 3
Private Const FILE_ATTRIBUTE_NORMAL = &H80 ' Normal
Private Const LOCKFILE_FAIL_IMMEDIATELY = &H1
 
Private Sub Command1_Click()
  Dim hFile As Long
 
  hFile = CreateFile("c:Eigene DateienTestFile.TXT", GENERIC_READ, _
    FILE_SHARE_READ, _
    ByVal 0&, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0&)
 
  LockFileEx hFile, LOCKFILE_FAIL_IMMEDIATELY, 0, _
                  FileLen("C:Eigene DateienTEstfile.TXT"), 0, ByVal 0&
End Sub