The way of availability Updated

Hi All,

I have observed that when a payment was completed room availability is updated. I used Paypal module to do the payments. I have observed form paypal IPN method data are inserted in to "uc_payment_paypal_ipn" table. In order to update the availabilty
it should update the "hotel_availability_calendars" table as well. But I'm unable to find the place where this is happening from the code. I need do my own coding stuffs when updating the "hotel_availability_calendars" table after done a successful payment.

Please guide me to how to do this.

Thank you.