Hello,

I need some help with a lookup function but I'm not sure of the best way to
set up my formula. The question I'm trying to answer based on my data is "How
many days have passed until the next sale of this product?" This is the
formula I'm trying to input in Column D.

Here's a simplified example:
(A) (B) (C) (D)
DAY OF YEAR PRODUCT SOLD AMOUNT (DAYS TO NEXT SALE OF PROD)
1 A 100 19 (DAY 20-DAY1)
6 B 50 34 (DAY 40-DAY6)
13 C 275
20 A 225
22 A 500
28 C 200
40 B 225


Thanks in advance for your help.
-Scott