Access VBA - Tweak Exisiting Code

Have an existing Access file that allows me to create a simple Windows Explorer type environment to view folders and files. (This is not my file but is allowed to be used as part of an application.) I need to be able to set it to a selected root folder. (Which will be always changing.) At the moment it automatically uses My Computer as the root folder, displaying C:, D:, E:, Etc folders beneath that. I want to it be able to set the root folder to, say, 'C:\Test' but I just cannot get it to use a chosen folder as the root folder. I wish to do this as I do not wish users to move up outside of the root folder, only down inside. So, in a nutshell, I need the Root folder of the left panel to be set via VBA variable to whatever I select. You can use any sub folder beneath C:\ as a test. The actual folder address, in practice, is a separate text feild assigned to each record.