Get total for account, for period

I'm using the API to pull data form e-conomic into an Excel sheet.
One row for each account number, one column for each month.
I currently use the ".GetEntriesByDate" function to get all entries for a date, the iterate these in order to get the total for the period.

This however can take quite a bit of time to get through, more that half an hour getting a full years data.

My question is this: Is there an other function I can use, to get the total for a given account number, for a given time period?

- So that I can avoid iterating all entries for the period, and hopefully save time.