paypal x-click-subscription mehtod use item variables - paypal

Question

this is my code:
<form action="https://www.sandbox.paypal.com/cgi-bin/webscr" method="post">
<!-- Identify your business so that you can collect the payments. -->
<input type="hidden" name="business" value="ram#gmail.com">
<!-- Specify a Subscribe button. -->
<input type="hidden" name="cmd" value="_xclick-subscriptions">
<!-- Identify the subscription. -->
<input type="hidden" name="item_name" value="Alice's Weekly Digest">
<input type="hidden" name="item_number" value="DIG Weekly">
<!-- Set the terms of the 1st trial period. -->
<input type="hidden" name="currency_code" value="USD">
<input type="hidden" name="a1" value="0">
<input type="hidden" name="p1" value="7">
<input type="hidden" name="t1" value="D">
<!-- Set the terms of the 2nd trial period. -->
<input type="hidden" name="a2" value="5.00">
<input type="hidden" name="p2" value="3">
<input type="hidden" name="t2" value="W">
<!-- Set the terms of the regular subscription. -->
<input type="hidden" name="a3" value="49.99">
<input type="hidden" name="p3" value="1">
<input type="hidden" name="t3" value="Y">
<!-- Set recurring payments until canceled. -->
<input type="hidden" name="src" value="1">
<!-- Display the payment button. -->
<input type="image" name="submit" border="0"
src="https://www.paypalobjects.com/en_US/i/btn/btn_subscribe_LG.gif"
alt="PayPal - The safer, easier way to pay online">
<img alt="" border="0" width="1" height="1"
src="https://www.paypalobjects.com/en_US/i/scr/pixel.gif" >
it have description option is item name variables but i want extra field in description..?
example: i use license type:1yr and perproduct: $10 * 12 month = $100..?
how to add this extra fields..?

Answer 1

Send a 'custom' field. Whatever you send in it will be returned as 'custom' in the IPN.