How to Catch Last Widget box From Same Widget Area?

Add the following code in your functions.php file of the theme directory. Replace widget name “Home Widget Area” with your widget’s name

    /*=============WIDGETs CSS CLASS CONTROLLER==============*/
    $GLOBALS['my_widget_num']=1;
    function edei_widget_class_adder($params){
    if( $params[0]['name']=='Home Widget Area' ){
        $GLOBALS['my_widget_num']++;
        if( ($GLOBALS['my_widget_num']%4)==0 ){
            $params[0]['before_widget'] = str_replace('class="', 'class="marginAdjust ', $params[0]['before_widget']);
        }
    }

    //print_r($params);
    return $params;
}
add_filter('dynamic_sidebar_params','edei_widget_class_adder');

function edei_widget_counter_reset($sidebars_widgets) {
   $GLOBALS['my_widget_num'] = 1;
   return $sidebars_widgets;
}
add_filter('sidebars_widgets','edei_widget_counter_reset');