I have a simple series formula looking like:

y=<FONT FACE="Symbol">S<FONT FACE="Arial"> (

**A** * c1^

**B** * c2^

**C** * c3^

**D** * c4^

**E**)

So, I have four input variables c1:c4 all being raised to a power from the vectors B,C,D,E. These vectors have roughly 70 entries, all integers from 0 to 6.

So, this looks like:

y=

**A(1)** * c1^

**B(1)** * c2^

**C(1)** * c3^

**D(1)** * c4^

**E(1)**
+

**A(2)** * c1^

**B(2)** * c2^

**C(2)** * c3^

**D(2)** * c4^

**E(2)**
+....

+

**A** * c1^

**B** * c2^

**C** * c3^

**D** * c4^

**E**
SUMPRODUCT does exactly that

y= SUMPRODUCT (

**A**;c1^

**B**;c2

**^C**;c3^

**D**;c4^

**E**)

The problem, well problem, is that these functions need to be evaluated in 10 cells, giving 10 different c1:c4's, but the same A,B,C,D,E. Secondly, these formulae are used iteratively in the sheet, without any VBA code. Array functions are

*much* faster that normal formula and evaluating these expressions at speed is important. A nice extra is that these formula are expressed in, if possible, 1 cell. The iterative routine is used to find a solution, Goal seek style. Goal seek is far too slow to be used, so a nice "circle reference" is used with a "smart" routine.

The SUMPRODUCT function is ideally suited for these operations, but because I use two different array lengths, one remaining to be evaluated per entry and one changing through the array, the SUMPRODUCT array function doesn't work. I have the feeling array functions and excel functions as SUMPRODUCT cannot function together by their very nature.

The sheet suffers from numerous invalid page faults and I'm trying to simplify it, or restricting memory use. The fault is an exception in Excel.exe (or dll) at module 167:etc, consistently with all users.

This message was edited by Foeth on 2002-09-25 23:45