give all you selectbox a class...say selectClass
and use jquery class selector.
try this
$('.selectClass').change(function(e){
alert($(this).val()); //gives you the selected value
alert($(this).parents('tr').find('td:eq(5)').text()); //gives you the related TD which is 4th column and gets its text
//or
alert($(this).closest('tr').find('td:eq(5)').text());
});