[Código Javascript] Conbox con nueva ventana

<form name="mycombowopt">
<select name="example" size=1>
<option value="url.es.tl">Tutoriales-seen</option>
<option value="http://url.es.tl">nombre link</option>
<option value="http://url.es.tl">nombre link</option>
</select> <input type="button" value="Go!" onClick="gothere()"> <br>
<input type="checkbox" name="windowoption" value="ON">abrir en nueva ventana?</p>
</form>

<script language="javascript">
<!--

/*Combo box with "open in new window" credit
-By Website Abstraction (www.wsabstract.com)
Over 200+ free scripts here!
*/

function gothere(){
var thebox=document.mycombowopt
if (thebox.windowoption.checked){
if (!window.newwindow)
newwindow=window.open("")
newwindow.location=
thebox.example.options[thebox.example.selectedIndex].value
}
else
location=
thebox.example.options[thebox.example.selectedIndex].value
}
//-->
</script>