select onchange trigger

select onchange trigger


guys help me please ...
i have select and options inside it .
every option has it own ID ...
how to trigger particula option in a way to call onChange of the
select here is small demo to explain better
<select name="somename" onchange="someFunc();
something.value=this.this.options[this.selectedIndex].id">
<option id="o_id1">text1</option>
<option id="o_id2">text2</option>
</select>
so i can select particular option but have no idea how to force
onChange of the select :(
        $("#o_id2").attr("selected", "selected");
Thanks.