Function to skip WooCommerce Checkout - Send Directly to Payment Gateway

Hi everybody, we´re a software development company and we´re building a tickets´ selling platform with woocommerce. We need a woocommerce expert to create a function to send the user directly to the payment gateway without going through the default woocommerce purchase funnel. We have created a custom purchase funnel where the user selects on a form quantity, payment method, seat location, and other data related to the event. That form is submitted through ajax to save the data related to the event, like the location of the seat, etc., and after saving I need to redirect the user to the payment gateway he chose before. In other words, I just need a php function or class that accepts these parameters: a) woocommerce product ID - which would be the ID of the ticket the user is purchasing. b) Quantity - Let´s say the user will purchase 10 tickets, for example. c) Payment gateway - We will use paypal standard and a custom credit card payment gateway. The function or class must return, not echo, a URL to make the redirection. The purchase must be received by woocommerce properly. I mean, we´re just skipping the purchase process, nothing else. With this function the user wont see the cart and checkout pages. He will be sent directly to paypal or the bank website to pay. Keep in mind we´ll use this function outside of woocommerce pages. This will be used when processing an ajax request. We could do this ourselves but we dont have the time, we need to develop other functionality of the platform while you do this. Max price is $30 USD. A Woocommerce expert can do this quickly. It´s just a php function or little class. At the end you´ll send me the php file.