Private podcasts

Hi-

I think I have the whole concept under control in terms of creating a 'subscribable' video podcast series.
But unclear whether or not I can make it non-public.
A client has asked that we create a video podcast out of internal employee communications videos we've done, so that employees can subscribe in iTunes... Since it's internal, we don't want the whole world gaining access to it.
I've seen the iTunes "block" function in the .xml code, but what exactly does this do?
Does anyone know how I can make sure that our feed doesn't show up in the iTunes podcast store?
Or if I add a user/pass on the directory where the feed lives, will that screw iTunes up?

Thanks-