SharePoint 2010 sub libraries or something similar
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I am trying to create a sub library structure with sharepoint 2010, however this seems to be impossible so I would like to somehow get similar functionality.

I have a library which can hold 4 content types. Let's say they are CT1, CT2, CT3 and CT4.
I have two folders. Folder 1 can hold CT1 and CT2, while Folder 2 can hold CT3 and CT4. I have set up custom views for each folder to make sure that only files of the desired content type are shown.

The problem is that when I try to upload a file, I need to select its content type and I can select any content type regardless of the folder I am in. This means that I can put a file with content type CT3 into folder 1. This file won't be visible but it will be there if i choose a different view. This means that a user can upload a file select a wrong content type by mistake and then be unable to access the file. 

Is it possible to restrict the types of files that can be uploaded by folder. So i can only  upload files of type CT1 and CT2 into folder 1 and files of type CT3 and CT4 into folder 2.

Thanks