Entourage vcs invites

[Steve Basile]

I use the web to download a fairly substantial number of events to attend.
These come to me as vcs files.

A good number of those events I would like to invite others to attend using
the Entourage invite tool. Regrettably, the Invite button is greyed out on
events created with vcs files.

Why am I able to invite people to events which I create but not invite
people to events which are downloaded as vcs files?

Thanks in advance.

Steve B.