Let me describe one of my current systems in this limited space. We have a couple hundred users running a VB app, each with its own Access database. On a daily scheduled basis or on demand (from user) the user sends some transactions to the central database on remote server. The server has a MySQL database and ASP page receives data from the remote users and sends entire user data back via FTP. The user sites contain between 3,000 and 35,000 records and it can take up to 2 minutes to update the local Access database.
We have a set of web pages which allow direct access to the central MySQL database. I could quickly give you (right know), web connection to your central Access DB.
This set up may not be right for you but it should show you that I could improve your scenario.
Thanks,
Langston