Possibly to add the comment field which appears when you select items can be much more easier solution if to implement the "year search" by other ways is too massive task.
like this:
(or for example such personal "exchange" comment can appear near the certain year / variety during selection if it's not emply and has the user's comment in)
to appear during selection from the swap list of the partner such note can be added here before, second comment line:
