I am trying to take the SUM of the number is the first row and divide by the COUNT of the cells that have numbers MINUS one of that COUNT.

Any ideas?

I can't attach a screen shot, but the data is monthly values. I want to compare the value of JUN (in this case 27) to the average of the preceding 5 months. I do not want to change manually the number of months in excel to divide by 5 as the COUNT functions bring 6. Attempts at formula simply subtract 1 from the average of the 6 months.