Modifying Google Search Form to Search XML Using Radio Toggle

I'm trying to modify the Google search form embedded in one of our XSL templates so that there is a radio button toggle to search the "Website" using Google or our XML "Faculty" directory with a PHP script. I have the Google code snippet:

<form id="SearchForm" action="{ou:pcf-param('search-results')}" 
 name="SearchForm">
                                    <div class="input">
                                    <input type="hidden" name="cx" 
                                    value="002701515966235043044:1yabqrtsqse" />
                                    <input type="hidden" name="cof" 
                                     value="FORID:11" />
                                    <input id="main-search" name="q" 
                                      type="text" placeholder="Search"/>
                                    <button class="btn" id="search-focus- 
                                     last" type="btn" aria-label="Search"></button>
                                    </div>

                                </form>
                                <script type="text/javascript" src="http://google.com/coop/cse/brand?form=searchbox_002701515966235043044%3A1yabqrtsqse"></script>

but am unsure how to modify it to allow for the additional behavior. I was going to add a fieldset after the /div:

<fieldset id="context-select">
     <legend class="sr-only">Choose to search:</legend>
     <label><input type="radio" id="context-website" name="searchterm" 
      value="website" checked="yes" /><span style="font-weight:normal;font- 
      size:medium">Website</span></label>
     <label><input type="radio" id="context-directory" name="searchterm" 
      value="catalog" /><span style="font-weight:normal;font- 
      size:medium">Faculty Directory</span></label>
</fieldset>

But am unsure where I would place action items for each radio button, etc. Thanks in advance for any help anyone can provide.