Sumif in powerpivot using a filter in a column with a parameter inside the same column

Hi,

I have this powerpivot table (I am using power pivots to avoid huge vlookups, so I have no choice)

In the table I have the number of seats booked each day for a specific departure day (we are talking about airplanes).

On example

Departure day - Booked day - No. of seats - incremental sales

30Jan16 - 1jan16 - 3 - 3
30Jan16 - 2jan16 - 1 - 4
30Jan16 - 4jan16 - 3 - 7
30Jan16 - 10jan16 - 5 - 12
30Jan16 - 12jan16 - 8 - 20
31Jan16 - 2jan16 - 1 - 1
31Jan16 - 3jan16 - 3 - 4
31Jan16 - 5jan16 - 6 - 10
31Jan16 - 15jan16 - 9 - 19

Question is, how to calculate the incremental sale column?

I was trying something like this:

=CALCULATE([Pax Count],BOData[DepartureDay]=[BOData@[DepartureDay]],BOData[BookedDay]<[BOData@[BookedDay]])

(where BOData obviously is the table with the data) but of course it does not work...

I was just trying to use the same reasoning that I would use with "sumif" (which does not work in powerpivot), but clearly "calculate" does not work the same way.

Thank you!

P.s.: using sumifs in the data source table is a no go... too many rows: it crashes the computer immediately