Nice one Harlan! I was going to offer the following...

=SUMPRODUCT(B2:B10,SUBTOTAL(9,OFFSET(C3:C11,ROW(C3 :C11)-ROW(C3),0,ROWS(C3
:C11)-(ROW(C3:C11)-ROW(C3)))))

....confirmed with just ENTER, but I prefer your formula. I'll have to
take a closer look at it so that I can understand it.

In article .com,
"Harlan Grove" wrote:

Darren Hill wrote...
...
So, for example, assume input column B and output column C, here's the
steps I'd need to do:
B2 * sum (C3:c11) +
B3 * sum (C4:c11) +
B4 * sum (C5:c11) +
B5 * sum (C6:c11) +
B6 * sum (C7:c11) +
B7 * sum (C8:c11) +
B8 * sum (C9:c11) +
B9 * sum (C10:c11) +
B10 * sum (C11:c11)
...

Use the array formula

=SUM(B2:B10*MMULT(--(ROW(C3:C11)<=TRANSPOSE(ROW(C3:C11))),C3:C11))