Just what is it you want to do? make a VB app to administrer an access database and upload that into the mysql?
That means opening up your database server to the evil internet world.
At least with a web interface you can use HTTPS and be sure nobody is listening in on your data.
Doesn't VB support MySQL directly? I know Deplhi has add-ons to connect directly to MySQL databases.
Another thing: a web interface is accessible from anywhere, your VB app would have to be installed wherever the client want's to work, and your app would have to be compatible with win98, winme, winNT4, win2k, winXP....
You'd probable have to communicate with the server on TCPIP ports that have been closed by the client's (or your) firewall.