I have a SharePoint document library that has a folder structure used for organizing the documents (but also for controlling access, via permissions on the folders).

The documents in the library are updated every month, and we store every month's version of the document in the same folder; there's a "month" column used for filtering that will contain values like Jan 09, Feb 09, etc. It looks like this:

    Title                  Month
    -----                  -----
    SubFolder 1
    SubFolder 2
[]  Interesting Facts      Jan 09
[]  Interesting Facts      Feb 09
[]  Interesting Facts      Mar 09
[]  Fascinating Numbers    Jan 09
[]  Fascinating Numbers    Feb 09
    ...

Now, because users will generally be most interested in the 'current' month, I'd like them to be able to apply a filter, and select (say) Mar 09. However, if they do this using the built-in filtering, it also filters out the folders, and they can no longer navigate the folder hierarchy. This is no good - I want them to be able to move between folders with the filter intact, so that they don't need to keep switching it off and on again.

I figured I might be able to use a custom view (selecting where type=folder or month=[month]), and to an extent that does work. However, I can only get it to work for a fixed month, whereas I need the user to be able to select the month - perhaps via a drop-down control on the page (and I don't want to create 60 views for 5 years' worth of months, nor do I want to have to create a new view every month).

I thought it might be possible to create a view in code (rather than via the UI), but I've not been able to figure out how to get a dynamic value (a user-specific setting) into the CAML query.

Any pointers gratefully appreciated! And by the way, I am aware of the dogma that folders are bad, and that everything should just be a list. However, having considered the alternatives, I still favour using folders - if I can solve this problem.

Thanks in advance.