payment gateway integration

hello, we need to integrate a payment gateway into our website built on social engine platform. since people purchase or pay for their tickets online on our website, we also need to create the correct path for the gateway + payment options. at any given point of time, there may be 2 or 3 events live and members need to pay for them using the payment gateway. they should be able to choose the event that they want to attend and then pay. besides this the testing of the gateway is also required before making it live. we need to make this live by the 12th of september 2012 so kindly send us your quotations fast. we request that only those people apply who have experience with social engine as well as payment gateway integration. applicants should also have worked enough on freelancer and should not be newbies. regards.