Nicht nur die Existenz eines Verzeichnisses können Sie prüfen,
     auch das Vorhandensein einer Datei können Sie ermitteln:

ERFORDERLICHE OBJEKTE

   -- keine -- 

FORM-CODE

   Const INVALID_HANDLE_VALUE = -1
   Const MAX_PATH = 260

   Private Type FILETIME
      dwLowDateTime As Long
      dwHighDateTime As Long
   End Type

   Private Type WIN32_FIND_DATA
      dwFileAttributes As Long
      ftCreationTime As FILETIME
      ftLastAccessTime As FILETIME
      ftLastWriteTime As FILETIME
      nFileSizeHigh As Long
      nFileSizeLow As Long
      dwReserved0 As Long
      dwReserved1 As Long
      cFileName As String * MAX_PATH
      cAlternate As String * 14
   End Type

   Private Declare Function FindFirstFile Lib "Kernel32" _
      Alias "FindFirstFileA" (ByVal lpFileName As String, _
      lpFindFileData As WIN32_FIND_DATA) As Long

   Private Declare Function FindClose Lib "Kernel32" _
      (ByVal hFindFile As Long) As Long

   Function FileExists(sSource As String) As Boolean
      Dim WFD As WIN32_FIND_DATA
      Dim hFile As Long
      hFile = FindFirstFile(sSource, WFD)
      FileExists = hFile <> INVALID_HANDLE_VALUE
      Call FindClose(hFile)
   End Function

   Private Sub Form_Load()
      MsgBox FileExists("c:\command.com")
      End
   End Sub