How to get SQL Server Name in an SSRS 2008 R2 expression

Hi, I am using SQL Server 2008 R2 and SQL Server Reporting Services 2008 R2. In one of my reports I am using an URL Action for a field. This report is currently deployed on the development server (Dev URL:http://devversion.com/). When we deploy this report on production this URL will change tohttp://prodversion.com/. I was looking for a way that I could write an expression by getting the SQL Server server name and report use it dynamically rather than change it manually.

Thanks in advance.............