How to clear cache values of select box which used AHAH concept

Hi everbody,

Could you please tell me how to clear previous data from the cache in AHAH concept?

Problem is, I make two dropdown(Country and State).When i select any country so it bind all related states to another select box(AHAH concept).Each time it contain these select box values into cache.After clicking the submit button, every cache value has to call.Means if you are using AHAH select box into 3 times.So submit button operation perform their task into 3 times.I don't understand why does it used previous cache values of drop down?

Thanx in advacne