Cancelling changes in a form – MS Access Version: 2003 (11.0)

On the form frmNz2 of my database, how can I make the Back button cancel any changes made to the information in the Search Results table after it has been editted? When I edit the information in the table and then press back, when the form is re-entered the changes stay. I would like these changes to be cancelled when pressing the Back button so that when the form is re-entered the table is the same as before changes were made (doesn’t save changes). I have tried making the macro for the Back button do this by selecting No when it gives the option of saving changes when exiting the form but it doesn’t work. I would be grateful for any help. Thank you.