Help to create a cumulative BEI from schedule data

I'm trying to automate a cumulative BEI chart from Microsoft Project schedule data. I'm new to Power BI and may be going about this the wrong way. 

BEI = (Total completed tasks)/(Total tasks planned to be completed by status date)

What I did:   

1.  I created two new columns for each month that I want to record the BEI. One for the calculation for the numerator and the other denominator. These columns populate either a 1 or a 0 for each schedule task, depending on conditions. 

2.  Created a new measure for each month.

                   Measure = DIVIDE(SUM('BEI'[Aug 20 Num]), SUM('BEI'[Aug 20 Den]))

3.  I drag each measure in order into a bar chart.

Problems:

1.  Power BI doesn't distinguish that each of these created measures are actually the same measure over time. Therefore, timescale doesn't show on the chart, nor does the cumulative trend line. 

2.  Many, many columns and measurements need to be made as time progresses. 

I've also created a new table with year and month to tie the measurement to the cell for the corresponding time. However, it looks like you can't put formulas into cells like you can in Excel. I'm trying to avoid using Excel as much as possible, because that would entail copying the entire Project schedule into excel each time you need an updated report.