Run Macro enabled Excel on server

Hi all,

Currently, I have developped an invoicing tool which I sell in my spare time to self-employed customers.
This tool is Excel based and has a lot of VBA code behind it, as well as ActiveX forms etc in the workbook.

I will install this excel file and make sure all the macro's are working (correct references checked etc) manually at the clients laptop/desktop.

So this is the current situation, but a lot can go wrong and it's time consuming.

Ideally, I want to move to a different situation of which I don't know it's possible.
In my head it's easy: I buy a server to host an excel for each client which they access through a web application that works with a user login.
By doing so, I can update their excel files remotely if I discover bugs or want to add functionality.
I should also be able to ask for a recurring fee to keep using the excel file.

Problems that I encounter:
- Is it possible to host macro enabled Excel workbooks? A quick google learned me that it's not so straight forward...
- what kind of equipment (server, software,...) would I need?
- There might be a privacy issue as their data is stored locally on my server and they might not like that I'm able to see all their data. How do other companies deal with this?

I'm afraid my IT knowledge is not sufficient enough, but I'm eager to learn and maybe I'll have to hire a professional to do this.
But if you guys can already tell me whether it's technically possible, that would be awesome!

Anyone?