[logback-user] attach additional rules to logback before it starts its configuration

Hello, Is there a way to add rules to interpret the data in logback.xml before logback starts its 1st initialisation, I want to add some specific parameters to logback.xml which i will use in my application specific logger Or is there a way to launch logback configuration on demand (not starts at the application starts) i can use JoranConfigurator but this means 2 times configuration Thanks