AppointmentItem.ForceUpdateToAllAttendees Property (Outlook)
Returns or sets a Boolean value that indicates whether updates to theAppointmentItem object should be sent to all attendees. Read/write.
expression An expression that returns an AppointmentItem object.
Normally, updates are sent to attendees only if the time or location of an appointment item is changed. Setting this property to True forces an update to be sent to all attendees, even if no changes to the time or location have occurred.