Prevent moving a calendar item

[Casper]

Hi,
Asked this at Outlookcode.com as well but got no answer, now I try here.

I've got an addin (form region) which (among other things) have
userproperties with dates which are the outer boundaries for the appointment.
I can handle in the addin that the user should not set start and end dates
beyond these boundaries but the user can still drag the appointment to
another date without my addin code checking. I've tried to use the
MAPIFolderEvents_12_BeforeItemMoveEventHandler delegate since it can be
cancelled but it only fires when moving the item to another folder. The
ItemsEvents_ItemChangeEventHandler on the items collection does not allow the
action to be cancelled.
Any ideas?

Thanks,