There must be a simple solution to this, but I'm having trouble finding
it:

I have two spreadsheets. One has daily sales totals that is updated
every day. The other references those totals, but adds them together
in a cumulative sum.

Sheet 1:
6/1 6/2 6/3
5 $10 6 $12 4 $8

On Sheet 2, I'd like to show cumulative totals:
6/1 6/2 6/3
$10 $22 $30

Problem is, on Sheet 1 I have an extra column in between each daily
total (quantity, as you can see in my "example")

Right now to get the cumulative total for a day I can reference the
previous day's cumulative total (in the immediately preceding cell on
the current sheet) and adding to it that day's daily total from the
other sheet. I can do this manually, but I don't have time to adjust it
for an entire month, times twelve different items.

Is there a way to adjust my formula so that I can just copy & paste it
across my sheet? What I need is a way to skip a column in my formula...