Im a complete newbie but I think you need an advanced search.
Try putting this in your header.php just above <div id="headerShortcuts"> it may give you a start?
<?php
echo tep_draw_form('quick_find', tep_href_link(FILENAME_ADVANCED_SEARCH_RESULT, '', 'NONSSL', false), 'get');
echo tep_draw_input_field('keywords', '', 'size="10" maxlength="30" style="width: 200px"') . ' ' . tep_hide_session_id() . tep_draw_hidden_field('search_in_description', '1') . tep_image_submit('button_quick_find.gif', BOX_HEADING_SEARCH);
?> </form>