Populating drop down list options dynamically using ajax

[eluser]Gukkie[/eluser]
Hi, i have got a problem trying to figure this out.

I have a Country Dropdown which contains countries, now when i select different countries, i need another dropdown called "state" to update the options according to the data retrieved, right now everything is working fine but how do i go about adding that data array to a form_dropdown()?

Any ideas?