How to use cookies

Hi

Ive got a problem. Ive got a script in php:

PHP Code:

---

echo '<a href="private_messages.php" target="rameczka">PM(';

if($i == 0)
{
echo $i;
}
else
{
  echo "<font color=\"red\">".$i."</font>";
}

echo ')</a>&nbsp;&zwnj;&nbsp;'; 


---

how to make a button in flash, showing PM ( number )? And make this button inactive, if cookie isnt set? And how will it (cookie) update - do i have to refresh page to chceck am i logged?