The mechanism you're looking for is called apt-pinning.
Forcing apt to do a downgrade is hard, it may be easier to uninstall the current version, and then pin and install the older version so that it's not upgraded until you want it to be.
Here's a howto:
http://www.debian.org/doc/manuals/ap...pt-get.en.html
the relevant parts are 3.8 and 3.10, but you'll want to read the whole chapter for background.
It's a Debian howto, but technically it would work just the same on Ubuntu.
But as Ubuntu is designed to resolve dependencies within a release, not across releases, there's no guarantee this will work.
Have fun.
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