Initiates when the field or subform loses keyboard focus, whether caused by a form filler action (tabbing to another field or clicking outside it) or by a script programmatically removing the focus.
You can use this event to provide verification of field data as a form filler moves the focus away from a field. For example, if a field requires a value, you can use this event to provide a message to the form filler indicating that the field requires some data before the form can be submitted.
See also 

exit event