how to access the names in text box from the database

hii al

i want to access the data from the database in a text box
according to the data from previous box ,, with out submitting


suppose,, we always do in filling data like...

selecting a country in a combo box ,,then we can see the
paricular state of that from the country are displayed in the next combo

how this???

you have to use some event on which you can fire java script code which will help you