Setting the Look and Feel only if not changed by the user

How can I set the look and feel to a specific look and feel, such as Nimbus, unless the user changes it to a different one such as Dark Nimbus using the options panel?  If I add code to set it in my installer class then it always gets run and overrides what the user changed it to.  Is there something I can add in my installer class to get the chosen look and feel from the user space?  Calling UIManager.getLookAndFeel() always returns the default so that doesn't help me.  I have been working on this for quite a while and I am soooo close to having this resolved.