This will require a bit of work on your part. Access cannot determine a record's last edited date - so you'll need to set it up yourself. The method I'll describe below explains how to capture the date and time of a records's last edit.
To report on a record's last edited date/time you need to setup your Form(s) to automatically capture that data and save it to the record at the time the change occurs. You'll need to create an additional field within your table(s) which will store this information. You'll probably want to name it something like LastModDateTime.
Then - Somewhere within your form(s) create an invisible text box named LastModDateTime and set its control source as the LastModDateTime table field.
Then - Create an AfterUpdate event for the form as follows:
Me.LastModDateTime = Now()
This will capture the date/time the record was modified.
On your report show the LastModDateTime field. Keep in mind that the date is captured on a record-by-record basis so if the report lists multiple records make sure you display the LastModDateTime for each one.
After you have your design implimented, you may want to go even further and create reports that show all records modified within the last month, last week, last 3 days, or whatever. For an example query used to capture this data - see this thread: thread701-595636
Hope that helps!
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Mike
In defeat: unbeatable. In victory: unbearable. -- Winston Churchill