can u tell me how to bind data to the dropdownlist?

Question

hi all,
can u tell me how to bind data to the dropdownlist box when i select STATE so and so MANDAL it shoulg reflet in another dropdownlist as i desinged database  
for example if i select MANDAL so and so villages should display in other dropdownlit box(4 dropdowns)

STATE
DISTRICT
MANDAL
VILLAGE

IN THE ABOVE FORMAT IF I SLELECT STATE DISTRICTS SHOULD DISPLAY IN DISTRICT DROPDOWNLIST BOC SO ON....
THANKS IN ADVANCE