Question for cascading dropdown

Sir,

I am working on Visual Studio 2005

I have three dropdowns.

- first is for Country

- second for states

- third for city

all three having separate tables in database. States related according countryid and City are related according coutryid and stateid

Now when i select country dropdown, state dropdown should populate according it and offcourse city dropdown too. But i want to avoid postback.  Would this be achieved by avoiding postback to retrieve there desired data?

hope you should do some needful.