How do we get multiple IPN for one paypal transaction using PHP?

Question

Hi,

   Am doing website using drupal, In paypal integration module am using PHP to pay amount in paypal(Your youtube video helped a lot)

  Let say in my site user planning to subscribe A, B and C option at a time
     A=10$
     B = 20$
     C= 30$

So totally 60$ user paid for all 3 subscription and site got IPN from PayPal.

Now user want to cancel one subscription(let say B), how do we cancel one subscription in this scenario?(because We got only one IPN id from paypal)

Please let me know if it is not clear and thanks in advance