Autopopulating form using multi column table (1 Viewer)

I have table with multiple columns that identify a location (ie. city / state / Country) that I use for filling in data on an Access 2010 Web Form. I would like to be able to pick a city and it auto-populate the state and country. I was able to do this easily on a client database but am having trouble making it work on a web form. Please help.

The web forms don't support the vba or other events.
Just wondering if using the primary key to run an Update Query might be the solution?
My guess is that the limitations of Web front-end will require more processing to happen on the back end (database).