This method is used to attach a message store handle created
outside of the class using the SocketTools API. Once the handle is
attached to the class, the other class member functions may be used
with that message store.
If a message store handle already has been created for the class,
that handle will be released when the new handle is attached to the
class object. If you want to prevent the previous message store from
being closed, you must call the DetachHandle method. Failure
to release the detached handle may result in a resource leak in your
application.
Note that the hStorage parameter is presumed to be a valid
message store handle and no checks are performed to ensure that the
handle is valid. Specifying an invalid message store handle will
cause subsequent method calls to fail.