Hi there,

I have a spreadsheet containing data representing a 3 dimensional data
structure in the following form;
Z1 Z2 Z3 Z4 ...
Y1 X1 X1 X1 X1
Y1 X2 X2 X2 X2
Y1 X3 X3 X3 X3
Y1 X4 X4 X4 X4
Y2 X1 X1 X1 X1
Y2 X2 X2 X2 X2
Y2 X3 X3 X3 X3
Y2 X4 X4 X4 X4
Y3 X1 X1 X1 X1
Y3 X2 X2 X2 X2
Y3 X3 X3 X3 X3
Y3 X4 X4 X4 X4
.... ....
and so on
In other words for every value Y (of which there are 8800 in total) there
are four X values and I have one set of data (8800 x 4) per month (with nine
years of data in total), so 3,801,600 data items in total (8800 x 4 x 12 x
9)

What I would like to do is average the four X values for each value of Y and
re-display it on a new sheet something like...
Z1 Z2 Z3 Z4 ...
Y1 Xm Xm Xm Xm ...
Y2 Xm Xm Xm Xm ...
Y3 Xm Xm Xm Xm ...
Y4 Xm Xm Xm Xm ...
..... ... ... and so on

However, when I construct the first line of the new file and then try to
drag it I don't get the right results i.e. if the first value of Xm is given
by AVERAGE(B1:B4) and the second is given AVERAGE(B5:B8), I actually get
AVERAGE(B2:B5). Even when I construct the first two lines of the file and
drag it I still don't get the right answer. How can I achieve this simple
action without having to resort to VBA? I'm sure I'm missing something
really obvious, so if I'm being a total noob please tell me :-)

Thanks in advance
Ian