creating a dynamic config file in C#

I am writing a windows service and have an appconfig file. I am trying to make it so I can modify this file outside of the compiled application. From what I understand, I can modify the exe.config file in the build folder where the application executable lives and change the value and save it. This should change the value but when I debug through the code, the value is still the original value and not what I just changed it to.. Does anyone have any knowledge of what I can do.... Is it because this is a windows service that maybe I can't modify the file outside the compiled application ? Help.... Thanks Carol