Power BI - share change at different levels of product hierarchy

[stsanders1]

I have 3 markets that account for all sales for current year and last year. I am able to use the % of row calculated field to see the share of each market for each product level, but I am looking to calculate the share change for each market vs. last year for each product level. So for Dept 2 it would be 0.34 (15.26 - 14.82), -0.38 (63.28-63.66) and -0.06 (21.46 - 21.52). Thank you.