How can I modify this code so that every time a Worksheet_Change event
occurs it will but the current date and time in cell (L1) over writing
the last update?

In addition win the files is open it show show the time of the last
update.

Private Sub Worksheet_Change(ByVal Target As Range)
If Target.Column = 11 Then
If IsEmpty(Target) Then
Target.Offset(0, 1).Value = Empty
Else
Target.Offset(0, 1).Value = Now()
End If

End If

End Sub