Is this what you were looking for ?
(Look at the green line in the chart called [View of Data] in the sample down below )
If yes, the formula I used in the Data table (you’ll find below the chart) in the field called [Cumulative Usage Sum] is:
Month <= thisRow.Month
(Note that Month is in fact CurrentValue.Month)
And what it does is :
It takes the whole list of rows the Data table is and from that whole list of rows (each row in the list being stored as/represented by CurrentValue), I ask Filter() to only keep the rows where CurrentValue.Month is less or equal than the value in thisRow.Month… which returns a filtered list of rows.
From the filtered list of rows, I can then dereference (access) their respective value in the field Usage transforming the list of rows in a list of numbers.
Sum() the values in the list of numbers .
I hope this helps !
Don’t hesitate if this is not what you wanted to accomplish ( ) … or if you have questions