questo è l'html...


<select id="sel1" size='1' name='id_volo' onchange="if (document.getElementById('sel1').options[document.getElementById('sel1').selectedIndex].value=='-----'){alert('Tutti i campi');};document.getElementById('1').disabled = false;document.getElementById('dep1').disabled = false;document.getElementById('arr1').disabled = false;document.getElementById('1').checked = true;">

<option>AC547</option>
<option value='delete'>-----</option></select>