Paypal IPN for trial Subscription how can I do it?

Currently I have an IPN script that works fine with, but my problem now how I can implement my script to work for a trial subscription.

For example, I will give 5 day trial to my new members for free, after 5 days it will automatically update the subscription to full membership.

How can I do that in my current IPN script, I really appreciate any help or link for an example.

here is my current code

if ($txn_type == "subscr_signup"  ||  $txn_type == "subscr_payment") {
      // insert subscriber payment info into paypal table

   if($payment_status=="Completed") {
	
           //Approve the members account
        
                                                            }
 
    }
	
else if ($txn_type =="subscr_cancel" || $txn_type =="subscr_eot"){


//Cancel membership and update it to free member only or expired
       
	 }
   

Code (markup):