I am using a selectbox:
<select name="priority" id="priority">
    <option value="4">Low</option>
    <option value="3" selected="selected">Normal</option>
    <option value="2">High</option>
    <option value="1">Emergency</option>
</select>
When user select "Emergency", then a confirmation box opens and if user confirm, then "Emergency" is selected. Otherwise "Normal" should be selected. For This, I am using jquery:
$(document).ready(function() {
    $('#priority').change(function(){
        if($(this).val()=='1'){
            if(confirm("Are you sure this is emergency?")){
                return true;
            }
            else{
                //here some code is needed to select "Normal".
            }
        }
    });
});
Now, How can I do that?