I'm trying to create a formula to derive the annual usage by our customers for a type of sales order. I need the formula to determine how much we sold a particular product to them, how many months of the year we sold it to them and then figure out that average. Then it needs to simply be multiplied by 12 to get the annual usage. However the only dimension for the chart is the year so I believe I need to use the aggr function in order to get the information I need by customer. Please see the formula below and let me know if you see anything I may be doing wrong.