Let's say that you have a spreadsheet with three fields, like:

Year Group Value
1970 1 3
1970 1 1
1972 1 1
1973 1 5
1974 1 2
1974 1 0
1974 1 2
1970 2 1
1970 2 1
1973 2 2
1975 2 3
1975 2 5

What I want is to combine all values for a given group in a single year.
So for instance, the above spreadsheet would become:

Year Group Value
1970 1 4
1972 1 1
1973 1 5
1974 1 4
1970 2 2
1973 2 2
1975 2 8

Any help on where to look as far as excel 2003 commands would be appreciated!