You need 2014, 2015, 2016, 2017 and 2018 all installed somewhere. That somewhere needs to have access to the 2014 data. Proforma from 2014 to 2015 (this only gives you a small portion of the real 2015 return, so you may want to add data to match real return). Repeat process(es) for 2015 to 16, then 2016 to 2017 and finally 2017 to 2018.

Direct input for 2018 might actually be quicker and easier.