Hi,

This may sound like the easiest question, but believe me its not. I'm
strugling with it for quite some time now.

Let me explain what is that I want. I have data for several customers
on their daily order values. Customers in rows and days in columns.
Say

day1 day2 day3 day4
day5 day6
cst 1 11 12 13
14
cst 2 11 12
13 15 16
cst 3 11 12
14 15 16
cst 4 11 12 13
14

Basically, I need the sum of their last 3 consecutive order values,
starting from most recent date (from right). So for cst 1 it would be
(12+13+14) for cst2: (11+12+13), cst3: (14+15+16) and cst4:
(12+13+14).

I suppose array formula should be of help but not sure how to do it.
Any idea can I get this done?