A control's sub procedure will not trigger the before update event of a form UNLESS it has some code to save the record (like DoCmd.RunCommand acCmdSaveRecord or If Me.Dirty Then Me.Dirty = True).
So, without you providing info from that event, you do not know which event may have done so. You could create a global variable which then you set the name when you have code that does that, and then read it in the Before Update event.