Hi, I'm working on a little project for my boss that involves averaging our daily sales data to create a sales projection for the upcoming week. Basically, I've been entering the sales from the previous day everyday. Every Monday morning, I need to average the daily sales from the previous week to project the upcoming week (for example, average the three pervious Monday sales to calculate projection for Monday, average the three previous Tuesday sales to calculate projection for Tuesday, etc etc).

I haven't used Excel since college a few years ago, so I'm a bit rusty. Previously, this job was done by keeping track of sales on scratch paper and averaging out each week by hand. I know there must be a way to create a formula that only averages only the previous three weeks data and updates automatically each Monday when I enter the previous weeks sales. I've tried a couple of simple AVERAGE() formulas, but they don't get the job done when I update with the sales log with new sales. Any help with this would be greatly appreciated. I know there is probably some simple solution, but for the life of me, I can't figure it out. Thank you for any help!!