Search using external sites Google Search
It's simple ,, if you know the HTML part so make your form action to the search site and call your GET parameters into the form!

something like this:

        &lt;form  action="bar.gov/gsearch" target="_blank" method="GET" id="search-block-form"&gt;
        &lt;input type="hidden" value="q" name="terms"&gt;
        &lt;input type="hidden" value="foo.com" name="search"&gt;
&lt;button type="submit" value="Search"&gt;Search&lt;/button&gt;
    &lt;/form&gt;


edit: you need to make sure you have HTML tags enabled and not stripped in anyway so the form and any other HTML tags be available .