I copied and modified the Flex 2 DateChooser control to achive the new functionlity. The swc is available here http://sreenivas.ramaswamy.googlepages.com/FlexEx2.swc.
I used this file to do the testing. I have done basic testing and it seems to work.
Only few dates in Jan, Feb and March of 2008 are enabled and it restircts the navigation to only those months
Currently I have made changes to only Flex 2 DateChooser. I would be happy to fix any bugs found !