In order to solve your problem you need to do the following steps. try to use procedures always 1)write a code for filiing countries name and can be placed in form load event. 2)write a code in that pass sql query as <select cityID,city from city where cityID=cmbcountryfilled.selectedvalue> and place this code in selection change commited event of country combo.and do the same for area.i ohope it will work. before that it depends how you are filling the combo.try to use dataset and fill the combo. please get back to me if you have any doubt...
