Display selected folder or item


This is a very beautiful treeview for displaying folders at the left site and items on the right site.
The only things that I am missing is to know which folder is selected at the moment. If some folders are opened and you go and come back you can not find quickly which of this folder are dispayled its content on the right site.
Is there any way to display the selected folder and item without modifing the source? or can somebody give me a quick tipp in which part of source I should modify?
I need a quick solution and therefore I appreciate any answer.