Count function with multiple criteria

[needhelp01]

I am currently struggling with a financial report that calculates an average that is based off a store count data item. I currently have two slicers. One is to return data from a specific company and the other is to return data from stores open that have been open a specified time period (comp). The store count data expression is count (1 within set (children ([Comp]))). The data returned is initially correct but is currently being divided by the wrong store count. I want it to be divided by the store count that is in the comp base and also in the specified company. Thank you for your help in advance.