Amazon/Ebay Price Fetcher Script/App

This project required a macro or script of some sort that will periodically surf and grab prices and other data from websites like [login to view URL] and Ebay. I have written an Excel macro that does this fine, but I need to add a few things, such as scheduling, e-mail notification of price changes, and possibly the ability to automatically purchase certain items if the price reaches below a certain point. Perhaps a scripting language such as Perl or Ruby would be better, but i personally don't know. My current Excel macro works like this: I have a sheet with a list of item numbers. The macro performs a Web Query using the URL and item number, and grabs the text i need (price) and inserts it into the sheet. If the price is lower than what i already have there, it hightlights the product number. It then moves to the next line and does this about 500 times. What i need now is for the program to e-mail me if it finds a price that is lower than what i already have in the sheet, or better yet, log in and but it right off the website. I also need the program to automatically run every half hour. There is also another website that I would like to do this with, but Excel web queries aren't compatible because the prices on the site are generated using AJAX. I don't care what scripting language you use or how this is implemented, it just needs to work and be flexible enough so that if these websites change slightly, I can readjust it easily if need be.