Thank you for all your help.
First, I need some sort of login function on the site.
The database functions will be:
Creating tables with specific datatypes (without the user knowing it of course. The user will only think of it as adding a selection criteria for instance). The PK and relations with other tables must be set by me. There will be 10 - 20 tables for each user. When ending a session I´m thinking the user saves all records and setting locally (in text files maybe) and empties the database. Next time the user is online, He/she uploads all the textfiles, turning them into tables.
So what I need is some sort of database "shell" that is empty until a user fills it with the imported text files. Of course another user shouldn´t be able to see the other users' databases. I think I need to do it this way, since only one of the tables will look the same for every user.
The functions I need are statistical functions (averages, trendlines etc), including some sort of yes/no box for disregarding a specific record from some tables.
Fuga.