I would like to track who opens a certain excel workbook. The macro below works great but only for those who have read & write permissions. It doesn't track users that have read-only permissions. Any ideas on the code? The uses must have read only permission.

Private Sub Workbook_Open()

Open ThisWorkbook.Path & "\TrackUsage.log" For Append As #1
Print #1, Application.UserName, Now, "Opened"
Close #1

End Sub