Hi Jakob,

Yes, you're right. When we open a file with Excel, the file is opened
exclusively and we could make use of this feature to check if the file has
been opened already. What we need to do is to try to open the specified
file. If an exception occurs, it means that the file has been opened.
Otherwise, the file hasn't been opened.

The following is the sample code.

Private Function IsOpen(ByVal filename As String) As Boolean
       Try
           Dim fs As System.IO.FileStream =
System.IO.File.OpenWrite(filename)
           fs.Close()
           Return False
       Catch ex As Exception
           Return True
       End Try
End Function

Hope this helps.
If you have anyting unclear, please feel free to let me know.

Sincerely,
Linda Liu
Microsoft Online Community Support

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