IsFileOpen bei schreibgeschützt-geöffneter Mappe??

Function IsFileOpen(filename As String)
Dim filenum As Integer, errnum As Integer
On Error Resume Next   ' Turn error checking off.
filenum = FreeFile()   ' Get a free file number.
' Attempt to open the file and lock it.
Open filename For Input Lock Read As #filenum
Close filenum          ' Close the file.
errnum = Err           ' Save the error number that occurred.
On Error GoTo 0        ' Turn error checking back on.
' Check to see which error occurred.
Select Case errnum
' No error occurred.
' File is NOT already open by another user.
Case 0
IsFileOpen = False
' Error number for "Permission Denied."
' File is already opened by another user.
Case 70
IsFileOpen = True
' Another error occurred.
Case Else
Error errnum
End Select
End Function