Help needed with fx Measures (Calculated fields) with Power Pivot

Hello,

I've asked this question a few times but I think I may not have been clear because I haven't received a reply yet. I am trying to create a dashboard for looking how my companies retail stores are performing. We have a lot of data so i decided to use Power Query/Power Pivot. I've gotten as far as being able to build the pivot tables showing this years sales and last years sales. I've done this in 3 different pivot tables to show last week performance, last 4 week performance and season to date performance.

What I can't do is build the measures/calculated fields to look at the year over year percentage growth for these metrics. Ideally, I'd like to have a an extra field in the pivot table that shows this. I've been stuck on this for a while so any help would be appreciated.

Since the companies finances are confidential info, I've taken a screen shot of how I have the "dashboard" (just a 1st step) laid out right now with the 3 pivot tables.

I also attached an example few lines of how the back-end data for last years sales, this years sales, and current inventory for the stores looks like in the data model looks like for reference.

Thanks for your help!