Totals by Month

I use the attached worksheet to manage payments processed from PayPal.
I am looking to save a little work in the automatic caluculation of the figures in Col I 113 - 123 and in J 113 - 123
The calculation currently is done with a manual auto sum
I have place next to the cells what I would like to achieve.

Also I am seeking an alert in Col E should a duplicate Invoice number be attempted.

Assistance appreciated