Auto search and purchase snipe like program for web store

Looking to get a simple (app, or script, or web app) programmed that will watch the listnings on [login to view URL] for certain parameters. For example characters over level 65 being sold for 100 RP to instantly be purchased on my account. This would work similar to a snipe tool on eBay except it would refresh the characters listings to immediately purchase. Looking for cheapest method to get this implemented. $30-60 budget.