How to Set XML Configuration File for Two different Environments

I have a separate XML configuration file for each environment (one for Test and one for Dev) in my package.

For instance, my flat file connection manager in DEV has a path\\xyz\dev\ABC.TXT

and in TEST , it is \\xyz\test\ABC.TXT

I need to use these separate configuration file in my SSIS package, so that when I select the "Configuration Manager" , I should be able to execute the package according to the selected environment.

I would appreciate it , if someone let me know how to do it.

ZK