triple integral using Simpson's 1/3 rule - Problem with finding particular arrays

Hello,

I've recently been able to compute double integrals using Simpson's rule in Excel VBA for both the following types:

1) ∫ ∫ eqn dydx x: between number and number; y: between number and number
2) ∫ ∫ eqn dydx x: between number and number; y: between x and 2x (as an example)

I'm trying to do the same with triple integrals using Simpson's rule in VBA.

However I'm stuck in finding particular arrays for computation.

It's difficult to explain. I've uploaded my excel vba file.

The sheet 2(2) contains the triple integral example in spreadsheet only.

The other sheets are just preparatory and not operational.

The VBA code is entered in Cell I3 in sheet 2(2).

The vba code will compute correctly all the arrays from M21 to AE53, that is, it got the answers for B24-27, B32-35, etc

I'm computing using loops 1 to N and (variables + loop *step size (a+m*h))

However i cannot find the other remaining arrays using this set up.

Can anyone help please?

Thanks

PS: The beginning of the code from "h2 = (f - e) / n" to "Next
Next"

is the tryout. The part that is ok and correct is below.