Using a combo box for a ajax search

I have a ajax search set up that works very well but I can only search
one thing.

code im using

Search: <input type="text" id="search_form" name="search" />

<img id="spinner" src="../images/spinner.gif" style="display: none;" />

<div id='results'></div>

<%= observe_field 'search_form',
            :frequency => 0.5,
            :update => 'results',
            :url => {:controller=>'ratings', :action=>
            :with => "'search_text=' + escape(value)",
            :loading =>
            :loaded =>
"document.getElementById('spinner').style.display='none'" %>

Where action is I was wondering if I could set up a combo box so I could
switch between methods in the controller and whats selected in the box
would be used for the action. I would can the moethods to make it more
meaning full for the user.