session problems....

i have a problem where i can only update the first name in my database details no matter whose logged in.here is the code.Any suggestions?

First part of the code
case 'detail':

echo '<p>
Please enter your details below.</p>
<form action="'.$_SERVER['PHP_SELF'].'" method="post">
<p>Price<br>
<input name="price" type="text" class="textBox"></p>
<p>Area:<br>
<input name="area" type="text" class="textBox"></p>
<p>Description<br>
<input name="description" type="text" class="textBox"></p>
<p><input type="submit" value="Edit Details" name="editdetail"></p>
</form>
';

break;

second part:

if(isset($_POST['editdetail']))
{
$username = $_SESSION['username'];
$price = trim($_POST['price']);
$area = trim($_POST['area']);
$description = trim($_POST['description']);
$do = mysql_query("UPDATE Users SET price = '$price' WHERE username='$username' LIMIT 1") or die(mysql_error());
$dotwo = mysql_query("UPDATE Users SET area = '$area' WHERE username='$username' LIMIT 1") or die(mysql_error());
$dothree = mysql_query("UPDATE Users SET description = '$description' WHERE username='$username' LIMIT 1") or die(mysql_error());

Is the username column unique?

next time can you wrap your code in the PHP tags. built in to VB.

when you mean uniqe do you mean that there only one name under username then no.should it be?