Non ho ben capito quello che vuoi.

Comunque....

codice:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

<html>
<head>
<title>Untitled</title>
</head>
<body>
<select name="selPatente" size="4"   class="selectForm" style="width:250" onclick="this.selectedIndex=-1"> 
<option value="A" >Patente A</option> 
<option value="B" >Patente B</option> 
<option value="C" >Patente C</option> 
<option value="D" >Patente D</option> 
<option value="E" >Patente E</option> 
<option value="F" >Patente F</option> 
</select> 

</body>
</html>