GDocs spreadsheets, how to do selective sums

Hey guys,

I'm creating a spreadsheet in google docs to keep track of how much money my gf owes me. I want to make a chart to see how the total changes through time.

In column A I have the date of an event and in column B the money spent (positive if I pay, negative if she pays). There may be several events for a given date.

In column C I want to put dates again, but without repetition, and in column D the sum of all the transactions of column B.

Pseudocode:

j=1
C[1]=A[1]
for i in 1..Nrows
  if A[i]==C[j]
    D[j]+=B[i]
  else
    j++
    C[j]=A[i]
    D[j]+=B[i]
  end if
end for

How the hell do I do that in GDocs?

>>4
Because a flat file and scads of Perl/awk snippets is a much more maintainable solution.

Any serious answers (that don't involve writing you own DB font-end, thanks very much)?