Custom field modified events

Is there a way to receive an event notification when a custom field on a
message is modified? The documentation says this:

"Recipients of a distributed item can modify only a small subset of that
item’s fields. For example, the personal subject and categories are the
only fields that can be changed by a recipient on a received message. An
event type of ItemModify is triggered on a distributed item when the
personal subject or category is modified."


But, in fact, users CAN modify custom fields, also (albeit not necessarily
by using the native GroupWise clients).

Is there a way to receive an event notification when a custom field
changes?

Thanks.

--sk.