That's because you're using the wrong tool.
The system that produces the .CSV file - it would probably be easier to get the summarised data extracted straight from there. Somebody must have written that extract, get them to change it to produce what you need, or get them to write another that does what you need.
Alternatively, MS Access is probably your best bet. Sucking the .CSV data into a table will create it for you. Creating a form using the form wizard that produces totals is quite easy. The form can just be copy 'n' pasted into whatever it is you are producing. Add to that a query to purge the table of records for re-use and the job's a good 'un for next time.