I have a large worksheet of sales data where products are down the rows and
months are across columns. I would like a formula to calculate the average
monthly sales but only inlude those months starting with the month of first
sale going forward. If a sale month is zero the cell is blank Example
worksheet:

Mo1 / Mo2 / Mo3 / Mo4 / Mo 5
Product 1 10 / 10 / 8 / 8 / 9 Avg = 9 (Avg includes all months)
Product 2 / 5 / 6 / 7 / 6 Avg = 6 (Avg excludes Mo 1 of zero)
Product 3 10 / / 8 / 7 / Avg = 5 (Avg includes Mo 2 & 5 of
zero)
etc

Any ideas? Thanks, Jim.