iCal and time zone

I have developed a AS to insert new entries from my travel itinerary directly into iCal and it works well. One small issue is that I need to edit the event in iCal to select the correct time zone for the specific flight etc.

Is there no way of setting the time zone during “make new event” or another utility / method to do this?

– Check if this entry must be added and Create the new iCal event entry

set dialogResult to display dialog ("Add this entry: " & the_event_subject) buttons {"No", "Yes"} default button "Yes"
if button returned of dialogResult is "Yes" then
	tell application "iCal"
		tell calendar "Travel"
			set theCurrentDate to current date
			set new_event to make new event at end with properties {description:the_event_body, summary:the_event_subject, location:"", start date:event_start_date, end date:event_end_date}
		end tell
		tell application "iCal" to activate
		show new_event
		-- delay 20 (*** I have this so that I can modify the time zone in iCal before inserting the next event ***)
	end tell
end if

Model: MacBook Pro
AppleScript: 2.0.1 (also use XCode(3.1) with AS2.1)
Browser: Safari 525.20.1
Operating System: Mac OS X (10.5)