Line Chart- Cumulative over time


My app is a simple 1 object app made up of 'funding report' records that list a date field, funding $ amount, and some other descriptors.

I can make a line chart showing a sum of the funds recorded for each month ($50 in Jan, $100 in Feb, $25 March, etc), but I can't figure out how to graph a cumulative total of funds per month ($50 in Jan, $150 in Feb, $175 in March).

I want to show a cumulative total per month as the year progresses instead of showing just the amount reported for that individual month. Any ideas? Sorry if this is an obvious answer and I'm just missing it.

Did you ever figure this out?