Accessing asset folder using file browser dialog

Hi,
I have a lot of database text files arranged inside folders and subfolders. I want to restrict the files from accessing externally from the app. So asset/ raw folder is the best option and each file size is less than 50kb. And in asset folder the arrangement is similar to file system and in raw folder its based on id's. So i opt for asset folder.
The selection of the database file is done by the user. So a search dialog window for browsing the file would be the better option. But i don't find any sample code for accessing a asset file system using dialog window. Is it possible?.

Thanks
Nikhil.