Read Appointment-specific Message properties?

[mesheree]

Found the answer in this thread... though I still have no idea what "casting" is. If anyone's Googling for the answer and finds this thread:

Basically:

1. Declare an empty Appointment object.
2. Loop through your Messages collection with a Message object.
3. When you find a message that has a ClassType of "GW.MESSAGE.APPOINTMENT", assign it to the Appointment variable.

Dim gwMsg As GroupwareTypeLibrary.Message3
Dim gwAppt As GroupwareTypeLibrary.Appointment9

Set gwCalMsgs = gwAcct.Calendar.Messages
For Each gwMsg In gwCalMsgs
   If gwMsg.ClassName = "GW.MESSAGE.APPOINTMENT" Then
      Set gwAppt = gwMsg
      ' ---< Now your object is of the 'Appointment' type. >---
   End If
Next

When I use VBA to read Messages from my GroupWise 7 Calendar, they seem to only have the properties of standard Message objects.
How do I gain access to a Message object's Appointment-specific properties?

Thanks!
Sheree