Category Dropdown Menu

Hi,

I want to create a search for real estate listings, basically I want to use a dropdown menu where the user chooses the State: QLD, VIC, NSW. If a user chooses for example, “NSW” the Suburb dropdown menu below the dropdown State menu will only show the Suburbs that I have listings for in the chosen State e.g Sydney.

They would then choose the suburb and click search and it would display the listings in that suburb.

If they choose a State and click search without choosing a Suburb, all the listings in that State should be shown.

For a better idea of what I want, go to http://www.carsales.com.au/all-cars/search.aspx?adv=1 and you will see “Make”, once you have chosen the make of the car, the next dropdown will then display the models of the car in the “Model” dropdown menu. This is the same concept.

Please help.

Cheers
Blake