Hi Kodjo - I looked at your website, and based on what I see, you must have a reasonable database system backing up your order system. I would be surprised if that system didn't already have some sort of reporting tool for your customers, but I guess that's possible.
A "drill down" tool would depend greatly on what system your data is in now. I would imagine (and I could be completely wrong) that there is some sort of export tool in the system you are using to take orders. If you could, say, export a record of your orders as a csv file, then maybe your analysis could just be in excel. That would be the quick and dirty way if your system doesn't have that reporting ability already.
If your system is contained within something that you have a bit more access to (i.e. if you have access to the tables in the database), you should be able to write a few queries to pull the info you need. For example, let's say you knew the tables and structure and it was in some sort of SQL dataset. writing the queries to pull customer/order date info would likely be fairly straightforward.