Advice on three dimensional array (difficult?)

[Tornados]

Hello, with two dimensions i seem to be able to do everything i want.. yet when they become three, things get more complicated. Please adivce on the following matters:

I have an array that contains two kinds of values , these values occur often and for each row i want the third dimension to act...so:

array(0 to 999, 0 to 1, 0 to 10) ' for example 11 rows, 1000 hits and 2 fields

then everytime something changes in column A from one of the 10 rows i want to add this number to the array in the right dimension and accordingly show the average of all values that have changed in the column A of the specific row.

1st i would like to know what the memory wise best way is to do this... it could be that there are 10 changes in row 1 (dimension 1) and 4 changes in row 2 (dimension 2).. How do i find the no of entries in the dimensions? if i understand correctly all dimension will have the same amount of elements .. so how do i get a correct average of these? I made it to work with two dimensions and to check which row it is yet i want it in 3 dimensions.


ie:
For x = 0 To ubound(array,1)
SUM = SUM + array(x, 2, row)
Next x
' will it be best then to check everytime whether an element has a value and then only add it?

2nd is it best to reserve memory in advance for an estimated amount of hits (999) in the example or make a dynamic one and redim each time an update occurs.

3rd and finally, is it only possible to refer to a dimension with a number or can it be text.. if for example i want to convert a text to a number can the array handle for example dimension 1500 when the rest is empty?

Tx! tornado