Hmm. Had to go look here: http://msdn.microsoft.com/en-us/library/cc895212.aspx

Beginning of the article ...

1. The /SET option of the DTExec command prompt utility.

2. Property expressions.

3. Package Configurations.

In essence, these three methods let you modify the values of package properties (like connection strings, variable values, network drive paths, etc) each time you run the package, without the need to edit the package in Business Intelligence Development Studio (BIDS).

Further down ...

#Consider using the indirect method whenever possible, as you won’t need to edit the package if the location or name of the configuration file change. With this method, the path and file name are stored in an environment variable.

#If you find that creating environment variables is too intrusive for your scenario, consider using the direct method. But be aware that changes to the file location may trigger changes to the package, or force you to usether options, such asthe /CONF switch on DTExec command line.

#You can override the configuration file path and name from the DTExec utility command line by using the /CONFIGURATION option. This option only affects the package being called from the command line; it does not affect packages executed via an Execute package task from a parent package.

So, is it this last line the question is referring too? Because reading the article as a whole left me thinking that I could make changes.