I have 2 view Helper for my form.

one for the date and other for the time. in my two view helper I have this code.

$view->headLink()->appendStylesheet(array( 'type' => 'text/css', 'rel' => 'stylesheet', 'media' => 'all', 'href' => $view->StaticUrl('/plugins/jquery/css/ui-lightness/jquery-ui-1.7.1.custom.css') , ));

When I use a date and a time element in the same form, the two helper are called and this css link is print 2 time in my header. headScript() work like a charme for that. I can print $view->headScript()->appendFile($view->StaticUrl('/plugins/jquery/jquery-1.3.2.min.js')); as many time I want it will only print it once in my header.