If you need the application to be usable over the internet and need the database to reside in a single place then you have two obvious options:
1. A web based application that talks to your database on its own LAN.
2. A desktop application that talks to the database thru web services. (This allows for an "internet enabled" application without the need to expose your database on a public IP address. You can make the web service require authentication or other kind of security measure to prevent unauthorized access.)
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Peter