Append Unique Data To Workbooks

I could use some help in modifying it so that instead of creating new workbooks to copy to, it copies to EXISTING workbooks whose names match the YEAR ("yyyy") in the Dates fields in column "B" (and only creates new workbooks for non-existing Years, IF needed).

Each workbook name is a "Year" (ie. 2000, 2001, 2002, etc.), and all unique data in A:D are to be copied to each corresponding Year workbook, again as per the Year in the Date field.

I’d like both columns "A" AND "B" tested to make sure that only original (non-duplicate) data is added to the corresponding Year Workbooks (all residing in one folder).

Btw, the code also copies the header, which is ok for new workbooks, but not needed for already-existing wbs.