TListView.OnEdited isn't triggered


I'm using TListView.OnEdited event to make some input checks and for an
'exists already'-comparison. Unfortunately, after having set
TListItem.EditCaption the user just presses the Return-key (which would
create a not allowed duplicate name), the OnEdited event is not
triggered. It's triggered only if the user had really changed something.
I need now a way to set the changed state to true, BEFORE or WHITHOUT
any real change. Perhaps using a message (but whith which parameters)?