Save
In the Before Update Event of the form you can put something like this:
Dim strMsg As String
strMsg = "Data has been changed"
strMsg = strMsg & "Save this Record?"
If MsgBox(strMsg, vbYesNo, "") = vbYes Then
'do nothing
Else
DoCmd.RunCommand acCmdUndo
End If
When the record has been edited and the user closes the form or goes to a new or different record, a messagebox will pop up giving the user the option to save the changes, or not.