Possible to automatically create a folder that only that user can see while using CreateNewUser control (and more related questions)?

I cannot figure out how to create almost two thousand named directories (I obviously need to automate this somehow) in my .NET website so that each person will be only able to see his/her own files. These are internet named user but won't be windows users.
I could  set up the 1000s of folders by hand but there has to be a better way.  I'm using .NET forms-based security.  
The most ideal would to be able to automatically create the user-named directory (folder) when I create their ID using the CreateNewUser control and then after I assign them to a role I could prevent them from seeing various folders but how would I automate letting them see their own folder only? Please let me know if I'm not being clear but essentially I want to automate:
1) creating the 2000 user-named folders
2) assign security so that each user can see his own folder but not the other users' folders
Thanks for reading and replying if you can help!
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