Managing a simple database by reading and creating text files

First let me say I am not confident this is the best way to achieve what I want, if you have any other ideas please tell me!

What I'm trying to do is a simple sales system, that contains a lot of clients and daily sales of products, and it's important that I work with the data of each client so I know what he likes most, etc.

The way I see it is that creating a new worksheet for each client is just messy and will eventually weight a ton, so creating a folder for each client and writing log files inside it keeping track of what he bought (all automated) , and then in Excel one could just choose a client's name, it would look up its log, do some regular expression and organize it in the worksheet.

I know how to do this in Lua and Java, but is it possible in VBA? basically writing/reading files as string and regular expressions

And what are the functions to do so? what should I look for?

Thanks in advance.

Why bother creating a file fore each customer?
I would create ONE database for ALL customers and a reporting system to allow you to only VIEW one at a time, if that is what you want.

If you have access or sql it might be better to set up a real database. Excel can still work with those.
Just my 2 cents.

Fair enough I'm happy to help resolve issues, but I'm not very good with reading and writing text files from excel in the way you need, so I'll butt out unless stuff comes along I can be useful on. Good luck!