Adding Global Parameters

Is there a way to access global parameters in Reporting Services Reports?..currently all we can usee is the Globals collection...is there a way to add keys to global collection?
can we write something in web.config ( as ReportServer is also a web application) and use the ConfigurationManager class?. The ConfigurationManager class did not work for me when I used it in the expression editor as the editor did not recognise it.

Any help is appreciated (or pointers for that matter).

Thanks.

Hello, have you found any solution yet? I'd like to use shared parameter of whole .net solution or project too. I could imagine to write assembly that expose a constant, but I wish it would exist an easier way. Jirka Nouza