Entourage events problem

Hi,
setting an event work fine this way. Why not deleting?

delete new_event to make new event with properties {subject:BrideGroom,
location:theLocation}

Also, when setting an event:
set new_event to make new event with properties {subject:BrideGroom,
location:theLocation}

How can I tell Entourage not to duplicate the event if it already exists?

Third question: How can I change the category of an event? I tried:

set theEvent to every event with properties {subject:BrideGroom,
location:theLocation}

set category of theEvent to (get categories whose name =
“WeddingsImageTemp”)

Thank you very much for your help

Ken