Dynamic configuration file name in select configuration type

I have created a package.  I have setup dtsconfig  file under

1. Package configuration wizard

2. select configurationtype = xml configuration file

3. Specify configuration settings directly

3a. Configuration file name = "C:\a\b\a.dtsConfig" 

This file consists of servername. When I move this package to QA, i see there we have a different path like "D:\a\a.dtsConfig". Due to this, am getting an error saying pathC:\a\b\a.dtsConfig not valid. How do I get / set path dynamically in "Configuration file name" text box?