Hi, 'required' option works on the add and edit pages only.
To check values on the advanced search page add custom JavaScript code for the 'Search' button. UseSearch page: Before display event on the Eventstab for this purpose. Here is a sample:
$xt->assign("searchbutton_attrs", "onClick=\"javascript: if (!document.getElementById('value_FieldName_1').value) {alert('FieldName is required'); return false;} searchController1.submitSearch();\"");