Excel divide by months until year end

Hello and thanks in advance

i have a sales sheet which staff record date, customer and recurring amount...

what i need is another column which works out the recurring amount by month left until end year (which is in cell z1, 31st may 2016)

Please note I am not great at excel.....but willing to learn

example

date                         Customer       Recurring

15 June 2015           AS                          2300
17 June 2015           BE                         17000
2 July 2015               CF                        25000

need

date                         Customer       Recurring    New

15 June 2015           AS                          2300      12 month left so total ok
17 June 2015           BE                         17000     12 month left so total ok    
2 July 2015               CF                        25000      I think i need divide by 12 then multiply by 11
2 August 2015         GH                      125000     I think i need divide by 12 then multiply by 10

etc

hope you guys can help