I recently won a reimbursment for a website I've been hosting for the past four years. I need to add up all the expenses I've incurred over that time period related to a particular instance (or set of instances). Right now the only way to do that is to download each invoice separately, month by month, for four years, and then total it up by hand. That's incredibly tedious.
A simple solution would be to let me specify an arbitrary date range, and a droplet filter, and you could generate for me a report of all transactions related to those droplets in that date range. Then I can import that into a spreadsheet and summarize it as needed.