Not exactly, but you can use your N78 to connect to the internet given that you can connect to the internet on your phone using your network (not WiFi).
Connect your phone via USB and select 'PC Suite'
Make sure that your version of PC Suite is the latest one in the web
When your phone is successfully connected and stable, open Nokia PC Suite and select 'Connect To The Internet'. Then click the settings icon (the wrench icon) and make sure to select the your Network Service. Then you can click 'connect' and you will use your phone's network to connect (via 3G, EDGE, GPRS). Standard rates apply as if you are using your phone to browse the web. So if you are on a Data Plan, you shouldn't have to worry.