SSIS 2008R2 - Use Package Config Value in Expression Is it possible to add a SQL Server package configuration value for an Expression attribute on, for example, a 'Flat File Connection Manager'?
Yes you can. In you expression you can use: "+@[User::(variable name)]+"

More info: https://anothersqlgeek.wordpress.com/2013/03/28/ssis-dynamic-connections-part-1/