<select size="7" name="D1" multiple>
    <option>1</option>
    <option>2</option>
    <option>3</option>
    <option>4</option>
  </select><

  echo "<form method=\"POST\" action=\"action.php\">";
  echo "<select size='10' name='link[]' multiple>";
  while ($row=mysql_fetch_array($result))
  {
    echo "<option value='$row[eintrag]'>$row[eintrag]</option>";
  }
  echo "

</p>";
  echo "</select></p>";
  echo "
";
  echo "

<input type=\"submit\" value=\"Abschicken\" name=\"B1\">";
  echo "<input type=\"reset\" value=\"Zurücksetzen\" name=\"B2\"></p>";
  echo "</form>";

$link = $_POST['link'];
echo "
";
if(empty($link[0]) OR empty($link[1]))
{
		echo "Bitte zwei Links anklicken! 
\n";
}
elseif(!empty($link[2]))
{
echo "Nur zwei nicht mehr auswählen";
}
else
{
print_r($link);
 }