[Código Javascript] Abrir boton en misma ventana o aparte

<form name="mycombowopt">
<select  name="example" size=1>
    <option value="LA WEB AQUI">TEXTO AQUI</option>
    <option value="LA WEB AQUI">TEXTO AQUI</option>
    <option value="LA WEB AQUI">TEXTO AQUI</option>
  </select> <input type="button" value="Vamos!" onClick="gothere()"> <br>
  <input type="checkbox" name="windowoption" value="ON">Abrir en ventana aparte</p>
</form>

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


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>

<option value="LA WEB AQUI">TEXTO AQUI</option>