This might suffice ..

In AB3, copied down:
=AVERAGE(OFFSET(B3,,COUNT(B3:U3)-1,,-12))

The above presumes each cell within the 20 col range (B to U) will be
sequentially filled each month from left to right with numbers (there should
be no blank cells in between)
--
Max
Singapore
http://savefile.com/projects/236895
xdemechanik
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"forest8" wrote in message
...
Hi there

Thank you both but neither of these worked.

I want this rolling average to always remain in the same column (e.g.
Column
AB). As I add each month, the rolling average will change accordingly.

Thanks
J