Hi
Ive been asked to work out the average temperature for each year from
1880-2007. So i have been doing this by adding the first 12 temp data and
then dividing by 12. But when i try to fill the the formula it doesnt
remember to add up the next set of 12. So i need to go from =sum(a1:a12)/12
and then change to =sum(a13:a25)/12 and then to =sum(a26:a38)/12 etc etc. If
anybody could help us with this it would save me loads of time
Cheers

Year Month Temp
1880 1 -5.2 17.7
1880 2 1.7 31.1
1880 3 7.6 14.5
1880 4 10.1 32.8
1880 5 13.2 11.5
1880 6 15.2 53.1
1880 7 19.1 42.1
1880 8 17.2 65.9
1880 9 14.6 56.8
1880 10 9.2 38.7
1880 11 2.9 64.5
1880 12 1.1 63.9
1881 1 -3.7 79.7
1881 2 1.6 33.8
1881 3 6 55.3
1881 4 9.8 16.7
1881 5 13.4 20.1
1881 6 16.8 16.1
1881 7 21 43.3
1881 8 17.9 129.8
1881 9 12.4 34.5
1881 10 5.7 34.4
1881 11 4.2 13.1
1881 12 -1.5 13.5