How to Change the Connection string in Config file created using Wix Setup

Hai,
   i have created One Setup using Windows installer XML(WIX)  (actually using Dark.exe and i have created the Wix source file from .msi file and now given the new paths to all the things) and it is successfully installed in program files.

    Now After installation i want to change the Connections string of sqlserver in Config file in the program file folder(which is project installed location). i tried that by modifying the Config file connection string in programfiles folder but after saving the running setup .exe it showing error like " the source has been changed you need to restart the installation"(it only takes the connection string path as at the time of installation).

    i have the requirement to change the Connection string in program file based on the Client location string. what will be the problem for that , is am i have to change any properties to change the connection string(dynamically) after installation.


Thnak you