problem with selecting parent element

problem with selecting parent element

Hi all,

I am doing a form with hidden fields which will be fired by select boxs or radio buttons,
all the hidden fields are wrapped by <span>

the problem is when the hidden field is next to select box like this:
EXAMPLE1
<label>Title: </label>
      <select name="title" id="titleSelect">
        <option value="">Please select a title</option>
        <option value="Mr">Mr</option>
        <option value="Mrs">Mrs</option>
        <option value="Ms">Ms</option>
      </select>
    <br/>
  <span><br/> <label>Please specify:</label><input type='text'  size='30' /></span>

$(this).next('span').show();            WORKS!!
$(this).next().show();                    WORKS!!


EXAMPLE2

< div class="selection"><input name="postGraduate" value="postgraduateYes" type="radio""/>Yes</div>
< div class="selection"><input name="postGraduate" value="postgraduateNo" type="radio" "/>No</div>
<span><br/> <label>Please specify:</label><input type='text'  size='30' /></span>

$(this).next('span').show();                        DOES NOT WORK :(
$(this).next().show();                                DOES NOT WORK :(
$(this).parent().next('span').show();            DOES NOT WORK :(
$(this).parent().next().show();                    DOES NOT WORK :(

$(this).parent().next().next().show();          WORKS, but when you click 'No' , it removes the wrong element.

What I want to do is targeting the next 'span' of current element, Can I possibly do that????
and have the statement like this

if(statement){
$(this).next('span').show();
}else{
$(this).next('span').hide();
}

BUT THIS DOES NOT WORK ON RADIO BUTTONS,

PLEASE HELP!!!