Question : loading contents on selection from select box

i have a select box where i show two modes

<select name="listings">
<option value="none" selected="selected">select one</option>
<option value="1">Premium Listing</option>
<option value="0">Normal Listing</option>
</select>

Now what i am trying is during initial page its should be showing the select one as it the default selection we have defined..

now when i click premium it should load another premium selectbox and if i use normal it should load another normal select box

so its just like swapping of the selectboxes based on the selection! please guide me in this

Answer : loading contents on selection from select box

Please see attached example: