Can I sum a list of value pairs by one element of the pairs?

Question

OK, I got a very helpful pointer to working around the time function limitations in Numbers.
Now what I have is a table that looks something like this (excerpt of course)
10/10/07 2:15 PM 0:30 0.50 $0.00 Design - Draft
10/11/07 9:30 AM 0:45 0.75 $0.00 Design - Revision
10/12/07 9:30 PM 0:45 0.75 $0.00 Build - HTML
10/13/07 8:45 AM 0:30 0.50 $0.00 Build - Copy writing
10/14/07 8:45 AM 0:30 0.50 $0.00 Build - Copy writing
I calculated the third (decimal) column with the formula =TIMEVALUE(B1)*24. Then I can use normal addition to sum the number of hours for a specific value of the fifth column (e.g. Build - Copy writing)
Of course the second row references B2, the third B3, etc.
Now what I would like to do is get a second table that looks like this:
0.50 Design - Draft
0.75 Design - Revision
0.75 Build - HTML
1.00 Build - Copy writing
So what I would like it to do is automatically generate a list of the values in the fifth column with a sum of the decimal values associated with that value in the third column.
Now I can do that by laboriously typing out a list of the values in the fifth column and using the SUMIF function. But then if I miss a value, or mistype a value, I will run into problems.
Is there a way to produce such a summary list automatically?
Any help would be greatly appreciated!

Answer 1

Yvan,
It appeared that there were probably a small number of categories, maybe six or eight, and if the Triton's list were hundreds, making an automated list builder seemed to be overkill. But to do so would require an additional column in the first table which would determine the list of unique categories:
=IF(COUNTIF(B$1:B2,B2)=1,MAX(C$1:C1)+1,"")
Then it's a matter of picking out those categories for the second table:
=IF(ROW()-1>MAX(Table 3 :: Hidden),"",LOOKUP(ROW()-1, Table 3 :: Hidden,Table 3 :: B))
Then the obvious SUMIF to get the values: =IF(A2="","",SUMIF(Table 3 :: B, A2,Table 3 :: A))
pw