Sending the selected option of a select via ajax


i want to create a form which contains 3 select-boxes which content depend on each other. i created the first select box:

<select id="timeblock_project" name="timeblock[project]" onclick="<%= remote function(:update => 'new_sub_project', :url => { :action => 'timeblock_submenu_tag', :id => ???}) -%> ">   <% for project in @projects %>     <option value="<>">       <>     </option>   <% end %> </select>

<td id="new_sub_project"> </td>

the :id => ??? should be replaced with the id of the project in the selected option-tag, but.. how?