ClickOnce & WebService Help.. Please!

Hi, I've been googling for a while trying to figure out how to solve this
problem, pleasy, I'll appreciate any sugestions.

I have a Winforms App that should work Online and Offline.

Online Mode.
Is the default mode and occurs when the App have an Internet connection. In
this mode the App connects to a SQL Server 2005 database using a XML Web
Service. Both WS and SQL Server runs on the WebServer wich also works as App
and Database server. The WS URL is stored on App.Config file.

Offline Mode.
Occurs in absence of an available Internet connection. In this mode the App
connects to a SQL Server 2005 database using a XML Web Service. Both WS and
SQL Server runs on the local machine and both are an identical copy of the
same services, running on the server. The WS URL is stored on App.Config
file.
When the user switch to offline mode the app changes the app.config and sets
the URL to localhost.


In both cases XML WebService works as a Data Tier.

The problem?
I'd like to deploy the App with ClickOnce to make the app easier to update
to remote clients and without loosing the Online/Offline functionality, but
I once the app is deployed with ClickOnce, I can't change the App.config
file.

Please help me. Any sugestions will be very appreciate.

TIA
Sergio.

PS.
VB .NET is used for the winforms and the WS