If your Excel Sheets are stored on a shared location and you also want to tracked who opened that Excel and Saved it then use the following steps.

1. Create a Sheet named "Log" with the following format.

Timestamp	Username

2. Copy the following code in the Workbook_Open Event

Private Sub Workbook_Open()
Worksheets("Log").Range("A65536").End(xlUp).Offset(1, 0).Value _
    = Format(Now(), "mm-dd-yy HH MM AMPM")
Worksheets("Log").Range("B65536").End(xlUp).Offset(1, 0).Value _
    = Environ("UserName")
End Sub