Tracking changes in a spreadsheet

You could use the workbook open event:

Private Sub Workbook_Open()
    
    Dim mySecretLog As String, FF As Integer

    mySecretLog = "X:\Secret\FileLog.LOG"
    FF = FreeFile

    Open mySecretLog For Output As #FF
        Print #FF, Environ("USERNAME") & " opened workbook: " & Now
    Close #FF

End Sub