Automated Website Item Purchasing

Project Objective: To purchase an item from an online site, as quick as possible, such as a bot. You could import a link into the program, of a list of filtered items, ranging from price range A - B, and being ordered by lowest price. I want the program to detect when an item of this list, is being listed at a price of my set value, or less. (So if items range from $50 - $200, the program detects when an item is listed at, say $10.) Once the item is detected, it select the item, and purchases the item. To purchase the item, it uses funds that are linked with the website, not through a credit card or Paypal. Assume these funds are already supplied on the site. Purchasing the item, consists of checking a box, and clicking a button. The items being displayed auto-fresh on the website, when a new listing is added that is lower than the current lowest price. I was told that the best way to accomplish this, would be to have the web-browser run internally within a program. Rather then having a program run on-top of a web-browser. I was also told that this could be coded through any language that deals with form applications. I do not have any preference in what language it's coded in, just that it operates efficiently, and quickly, as time is a factor when purchasing.