The method I use is create a timestamp.
In the tables that you're using, create a date field. Even better, two date fields.
One that is called, timestamp and one called modified_rec.
The timestamp field is easy. In the default value you simply put, Now() and it will put the date and time that the record is entered. For modified, I would say, leave that blank and do some VB code.
Code:
Private Sub Form_Dirty()
' If the record gets edited in anyway, record the date and time.
modified_rec = Now()
End Sub