Best solution to update the applications

[nano2k]

Hi

I'm developing a client/server sistem (based on .NET Framework 2.0
(C#) using VS 2005):

1. A webservice
2. A client WinForms application.

Classic.

Now, the client app will be installed in many locations and will
access the webservice.
I want 2 things:

1. The client app and the webservice should be "version compatible".
That means, if the webservice is version 1.5.1.2340 (including the
build number), it should work ONLY with 1.6.2.3456 version of the
client application.

Trying to access the webservice using a different version of client
app should deny the access.

2. Automatically upgrade the client application(s) so there's no need
for another qualified person to install an update. I imagine that the
webservice should provide the update package to the client app, the
client app should download it and install it automatically (this means
even registering COM dll's, etc). After the update process, the
webservice should accept only connections from the client application
having the right (the new) version.

Which format should the package be? Is there a standard scenario for
such operations?

The webservice and the client will communicate through secured VPN, if
this should matter in choosing the right solution.

Thanks.