I need to sum (entered as array in one cell) a series of cells that go up
multiplied against a series of cells that go down.

I have a row of four cells
A B C D
Row 1 2 5 3 6

and another row
A B C D
Row 3 1 2 3 4

the formula I need (my attempt at which is:
=SUM(A1:D1*OFFSET(G28,0,-1*A3:D3+1))

should do the following:
multiply A1*D3
multiply B1*C3
multiply C1*B3
multiply D1*A3

and sum them up.

Where am I going wrong?
--
Boris