MTD(Month To Date) calculation in script

[Tatynout]

Good day, 

I would like to make a MTD (monthly to date) calculation of data by cumulating monthly data from 2018 in QS script. 

Here is an example of the calculation in Excel:

Here is how the data should be represented in QS for every year:

I please need  help to calculate my  MTD field into QlikSense script. 

I have attached the excel file to this post.

Thanks for your help.

Tatiana