Saludos 
Me refiero al tag html <select>
este es mi codigo
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "
http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title>Documento sin título</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<script language="javascript">
	function RellenaLista(formulario)
		{
			obj=document.getElementById('lstLista');
			if (obj.selectedIndex==-1) return;
			valor=obj.value;
			txt=obj.options[obj.selectedIndex].text;
			obj.options[obj.selectedIndex]=null;
			obj2=document.getElementById('lstRecibe');
			opc = new Option(txt,valor);
			eval(obj2.options[obj2.options.length]=opc); 
		}
	function BorraUnoLista(formulario)
		{
			obj=document.getElementById('lstRecibe');
			if (obj.selectedIndex==-1) return;
			valor=obj.value;
			txt=obj.options[obj.selectedIndex].text;
			obj.options[obj.selectedIndex]=null;
			obj2=document.getElementById('lstLista');
			opc = new Option(txt,valor);
			eval(obj2.options[obj2.options.length]=opc);    
		}
</script>
</head>
<body>
<form name="form1" method="post" action="">
  <table width="50%" align="center" >
    <tr>
      <td width="22%" rowspan="4">Producto</td>
		<?php
			include "conexion.php";
			mssql_select_db("Bd") or
			print "No se pudo conectar a la Base de datos";
			$result = mssql_query("select usu_Cedula, usu_Nombres from Usuarioss order by usu_nombres",$conexion);
			mssql_close($conexion);
		?>
      <td width="32%" rowspan="4"><select name="lstLista" size="6" id="lstLista">
          <? $cont =0; while($row=mssql_fetch_array($result))
					{ 	
						echo "<option value=".$row['usu_Cedula'].">".$row['usu_Nombres']."</option>";
						$cont = $cont + 1;
					}
				?>
        </select></td>
      <td width="6%"><div align="center">
        <input name="btnUnoAde" type="button" id="btnUnoAde" value=">" onClick="RellenaLista('form1');">
      </div></td>
      <td width="40%" rowspan="4"><select name="lstRecibe[]" size="6" id="lstRecibe">
        </select>
        <input type="button" name="Submit" value="Botón" onClick="form1.Accion.value='va';submit();">
        <input name="Accion" type="hidden" id="Accion">
        <input name="Valor" type="hidden" id="Valor"></td>
    </tr>
    <tr>
      <td><div align="center">
        <input name="btnUnoAtr" type="button" id="btnUnoAtr" value="<" onClick="BorraUnoLista('form1');">
      </div></td>
    </tr>
    <tr>
      <td><div align="center">
        <input name="btnTodAde" type="button" id="btnTodAde" value=">>">
      </div></td>
    </tr>
    <tr>
      <td><div align="center">
        <input name="btnTodAtr" type="button" id="btnTodAtr" value="<<">
      </div></td>
    </tr>
  </table>
  <input name="btnCont" type="button" id="btnCont" value="cont" onClick="contador()">
<script language="JavaScript">
function contador()
	{
		var num='<? echo $cont?>';
	    for(a=0;a<items.length;a++)
		alert(num);
	}
</script>
</form>
</body>
</html>
<?php
	if($_POST['Accion']=='va')
		{echo $cont;
		$Var = $_GET['lstRecibe'];
		foreach( $Var as $value)
			{
				echo "item".$value;
			}		
		}
?>
Agradezco de antemano la ayuda que me prestas