The scenario:
User A has sent a meeting request to user B. User B has accepted this and 
the meeting is stored in user B's private calendar.
Then user A sends a cancellation and user B receives a special message 
stating this fact. In Outlook you then get a button which reads "Remove 
from calendar" in order to remove the meeting from user B's private 
calendar.

But how to simulate this last "remove from calendar" trick 
programmatically (in for instance VBScript) when logged on and 
authenticated as user B?
I know how to retrieve the actual Appointment object from the message, by 
iterating through the CalendarParts collection and then running the 
GetUpdatedItem method of the CalendarPart.

I also know how to delete a specific calendar entry (when I know its exact 
UID) by doing lots of mumbo jumbo involving the following code:
*** START CODE ***
set rcAppointment = Server.CreateObject("ADODB.Record")
set rstAppointment = Server.CreateObject("ADODB.Recordset")
set rcDeleteApp = Server.CreateObject("ADODB.Record")

rcAppointment.Open strCalendarURL
set rstAppointment.ActiveConnection = rcAppointment.ActiveConnection
rstAppointment.Source = _
	"SELECT * " & _
	"  FROM scope('shallow traversal of """ & strCalendarURL & """') " 
& _
	" WHERE (""urn:schemas:calendar:uid"" = '" & strUid & "')"

rstAppointment.Open
if not rstAppointment.EOF then
	set rcDeleteApp.ActiveConnection = rstAppointment.ActiveConnection
	strCancelItemURL = rstAppointment.Fields("DAV:href").Value
	rcDeleteApp.Open strCancelItemURL, , 3 'adModeReadWrite
	rcDeleteApp.DeleteRecord
end if
*** END CODE ***

The problem is that I can't use the second method when all I have 
available is the Appointment object. As far as I can see, there is no UID 
to retrieve anywhere from it.
I guess I could always instantiate a Cancel object (with the 
CleanupCalendar flag set) from the Appointment object and send it off to 
the organizer, but that's fairly contradictory to what normally happens in 
Outlook.

Anybody feel up to some serious problemsolving?

Ehem, the solution is actually embarassingly easy ;-)
Once I've got the Appointment object, it's all just a matter of retrieving 
the correct value from the everpresent but oh so strange Fields 
collection - something I've even done earlier (shame on me....).

The code evaluates to nothing less than:
strMessageUid = objAppointment.Fields("urn:schemas:calendar:uid")

I then use this Uid in my code for deleting the correct calendar entry.

Case closed.