Need to create a formula similar to MS Excel.

Basic logic is:

Sum all values in C where A = x and B = y

This is done to produce a sheet of consolidated sums from a sheet with an ongoing set of log entries.

LOG:

DATE TIME ACTIVITY

2013-01-06 :25 finance

2013-01-06 :42 systems

2013-01-06 1:13 finance

2013-01-06 :23 systems

…

SUMS:

DATE finance systems

2013-01-06 1:38 1:05

…

So the formula becomes something like:

sumif(LOG.$A:A=$A2 AND LOG.$C:C=$B$1; LOG.$B$2:B)

Any suggestions?