Program that refresh and add to cart

First of all is not required a specific programming language you can make this software how you want This software have to work on a website that i'll link in private and have to hit a link. The link will not be online for public so hitting it we will be redirect to another page. So the program have to hit the page in a interval of time that i can choose but anyway it must be from 0.1 sec to 5 sec. Once the link is online the program have to choose the size of a product, add it to the cart and then go to the checkout and if possibile make the checkout. I'll show this steps in private. This data must be editable by me everytime i start the program : - interval to hit the link - login datas for this website - Size to choose - normal shipping or express shipping - payment method - data for checkout ( if it is possible )