Vacation tracking from an anniversary date from year to year

I had trouble coming up with a formula that would split networkdays if vacation started on one side of an anniversary and ended on the other so decided on a manual approach. If the user is entering the vacation dates on "Data" tab and it crosses the anniversary, the entry will turn red. Then the user should split the entry into two lines. First one up to but not including the anniversary date, the second one from anniversary date forward. (I did this on lines 2 and 4). Column F shows the anniversary date (updated to the year of entry).

I also included a Partial day column (D) where you put in hours of vacation on a partial day. This is inclusive of the dates in B and C. So on 10/21/2015, Employee A came in and worked 6 hours and then went home (2 hrs vacation)

Hope this helps. Questions?