Codice completo:
codice:
<SCRIPT LANGUAGE="JavaScript">

<!-- 

function sendValue(s){
var selvalue = s.options[s.selectedIndex].value;
window.opener.document.Myform.campo.value = selvalue;
window.close();
}

// -->
</script>

<script language="JavaScript" type="text/JavaScript">
<!--
function convalidaForm(Myform) 
{

 
  for (var a = 0; a < Myform.elements.length; a++) 
	{
	var campo = Myform.elements[a];

      	if ((campo.value == '') || (campo.value == 'undefined')) 
		{
        	window.alert('Il campo ' + campo.name +'\nč un campo obbligatorio in questo form.');
        	campo.focus();
        	campo.select();
        	return false;
      		}
      		
      		
        }
 
      
  // Abilita l'invio del FORM
  return(true);
}
 
//-->
</script>

<form name=Myform>

<select size="1" .....>
                      <option>Selezionare valore</option>
                      <option value="...">valore</option>
                      .....
                      .....
                      </select>

<input type=image src=../img/invia_button.gif onClick="sendValue(this.form.campo);" width="84" height="16">
<input type=image src=../img/annulla_button.gif onClick="onClick=window.close();" width="84" height="16">

</form>