web.config Server.MapPath connection string

Hi,

I'm new to Asp.NET, up to now have been using plainold ASP.

Is it possible (YES or NO) to use the Server.MapPath function in the Web.Config file?

I'm asking for the obvious reason of not having to change everything when I copy files from my test server to a live site.

Right now on my ASPX page, I have:
Dim connectionString As String = ConfigurationSettings.AppSettings("ConnectionString")
Dim dbConnection As System.Data.IDbConnection = New System.Data.OleDb.OleDbConnection(connectionString)

and in my Web.Config file, I have tried to use :
<appSettings>
   <add key="ConnectionString" value="Provider=Microsoft.Jet.OLEDB.4.0;Ole DB Services=-4;Data Source=" & Server.MapPath("data\mydatbase.mdb") & ";" />
</appSettings>

This gives me an error message.

If it is NOT possible to use Server.MapPath in the Web.Config file, do I have to use something like :
<appSettings>
   <add key="ConnectionString" value="Provider=Microsoft.Jet.OLEDB.4.0;Ole DB Services=-4;Data Source={0}" />
</appSettings>

and then how would I call that from my aspx page:
Dim connectionString As String = ConfigurationSettings.AppSettings("ConnectionString")????????

thanx for any help!!