problem with gridview

Question

i have empid ,name ,sal,state,city in the table emp..iam binding emp table to gridview ...iam using dropdown list for states and cities....if i select a state automatcally cities has to come for that particular state...my question is while i was updating a row in gridview automatically dropdown list has to bind in edit item template and if i select a state automatically cities has to bind for that particular state...while i was updating states and city's has come from database ....how to update pls help me its urgent