Previous Month Value

Hello Experts!

For the simple calculation I'm trying to achieve there should not be any major issue, however, I keep trying in so many different ways suggested online and still finding no success here. Hopefully an expert here will help me get to a solution:

I simply want to make a PREVOUSMONTH operation!

On the file below there is a list of projects that achieve a % Complete every month. The extra column that I added called % Progress is the difference between the % Complete of the current month and the % Complete of the previous month. I achieve this in Excel using VLOOKUP very easily (there are over 400 projects reporting progress every month).

Ultimately I want to create a matrix as per the second below

But I am just ok if I can replicate the % Complete of the previous month on a separate column (% Complete Prev), then I would simply subtract % Complete - % Complete Prev

In Power Bi I have got as far as the measure below but receiving no values back:

% Complete Prev = CALCULATE(MAX(Sheet1[% Complete]),PREVIOUSMONTH('Sheet1'[Date]))

Any ideas will be hugely appreciated!

Best,

     Ricardo