Chris:

Your results look better than mine. Your projected sales for the year = 240 which makes sense.

But what if you are at the end of the first month of the year? YTD equals 20 (change cell E3 to 20) and the new projected sales = 170. Based on the 13 months of history, you would expect it to remain at 240

Your idea (3 different indicators) is good. But they aren't that different. For instance, in month #1 of the year, you only have one month of YTD and 12 months of LY. Those 13 months are identical to the 13 Period figures (assuming year-end and period-end figures are run on time). In month #12 of the year, you have the 13 Periods plus 11 months of LY.