Implementing Role Based Security On Subfolder

Hi all, suppose my project root folder contains three sub folders; namely Sales, VIP, and Vital Resources. My focus is on the VitalResources folder and the following is a tree view of  this folder.
                         [Sales]----------[Root]----------[   VIP  ]
                                                      |                                                      
                                         [Vital Resources]---------Database_file
            &nb ...