This sheet shows you sub category-wise
1. Last Year running sales
2. Current year running sales
3. An indicator when CY Sales < LY sales
You would start with creating the calculated fields that show you the sales for last year and current year. And then to add a bit of interactivity and put it in the hands of the user, you would create a data parameter and show its control.
To get the red alert, they created a calc called YTD difference, put that on Label and colored it red (the way the calc is written only shows if the condition in the calc is met)
Does this explanation help? or if you can elaborate what you dont understand specifically, I will try to address that.