calculate the avarage by referred column and answer in qontinous column

[deli]

i want to average the data from the cell but referred to the number of group from different column like below

A B C
group_no value
1 20
1 23
1 23
1 21
1 22
2 24
2 25
2 27
2 29

i need to calculate the answer in column c in continuous of beside the value but the average must separate by group_no
i try this IF(A1:A9=1,B1:B9)), but it will only give the answer for group 1, i have about hundred of group no to handle.
kindly help me please.
tq

 

[GlennUK]

How about doing this with a PivotTable?

 

[deli]

pivot table?

 

[Marcelo Branco]

Take a look at

http://www.timeatlas.com/tutorials/excel_pivot_tables.pdf

or

http://www.timeatlas.com/5_minute_t...e_pivot_tables_in_excel_2007_to_organize_data

or


http://chandoo.org/wp/2009/08/19/excel-pivot-tables-tutorial/


M.