Hi Bernie,

My formula does not change with different values ...

It is just that:
If I have 3 periods (Column C, D, E -row19), as in the above example.
Then I should multiply the corresponding product
on row 21 (and down...) with
INDEX(SOURCE;MATCH($A$20;INDEX(SOURCE;;1);0);MATCH (C$19;INDEX(SOURCE;1;0);0))
INDEX(SOURCE;MATCH($A$20;INDEX(SOURCE;;1);0);MATCH (D$19;INDEX(SOURCE;1;0);0))
INDEX(SOURCE;MATCH($A$20;INDEX(SOURCE;;1);0);MATCH (E$19;INDEX(SOURCE;1;0);0))
respectively.

To get a result in F21, G21, H21

IF I have 4 periods: C-D-E-F
Then I should multiply the corresponding product on row 21 with
INDEX(SOURCE;MATCH($A$20;INDEX(SOURCE;;1);0);MATCH (C$19;INDEX(SOURCE;1;0);0))
INDEX(SOURCE;MATCH($A$20;INDEX(SOURCE;;1);0);MATCH (D$19;INDEX(SOURCE;1;0);0))
INDEX(SOURCE;MATCH($A$20;INDEX(SOURCE;;1);0);MATCH (E$19;INDEX(SOURCE;1;0);0))
INDEX(SOURCE;MATCH($A$20;INDEX(SOURCE;;1);0);MATCH (F$19;INDEX(SOURCE;1;0);0))
To get a result in G21, H21, I21,J21

and this down for the number of items in column B.

Does this make more sense??
If not, I'll try again ;o)

Sige