Ebay Auction Launch/ Tracking w/ API Needed

We operate a drop-shipping program for eBay sellers. With our existing system, our registered sellers reserve inventory in our warehouse for marketing, launch auctions and send us payment for the item and the shipping label when they have been paid on an auction closing. We ship to their customer directly. Our existing system is programmed in ASP code using VBScript to manipulate data an Access database. At some point, we will need to transition to a SQL database format as we scale the operation up. The database has several tables: Agent Contains all information regarding authorized sellers, usernames & passwords, eBay ID’s, etc. Items Tracks all relevant data regarding the items in the warehouse. Indexed by SKU number and cross-referenced with UPC’s. Contains price, cost, inventory levels and filenames for product photos (the photos are stored on the Web server). Orders Contains information for the Purchase Orders of restocked product. Sales Tracks sales of items. Presently, our sellers log into the system and reserve an item for marketing. This is a simple function that moves one item from “OnHand” in the Items table to “Reserved”. When it is sold, the seller enters the sale data and the item is moved from “Reserved” into “Sold” in the Items table and the sale details are recorded in the Sales Table. OnHand, Reserved and Sold are number fields tracking the unit counts for a particular SKU. The problem we have is that we cannot monitor if our seller actually launches an auction when an item is reserved, and the reservation does not cancel if the auction is ends unsuccessfully. We know that our sellers are reserving items that are not presently at auction, which ties up inventory at our warehouse. It also is presenting a problem for our sellers in that they need to manually update their product reservations. We need to create an API with eBay that allows us to tie an auction number on eBay with a reserved item on our system. It would make sense that when a seller reserves an item they are doing so in the context of launching an auction or posting an item to their eBay Store. If we are going to the trouble of programming an API launch tool, we should probably also program an auction monitor as a tool for our sellers. Since we already have the item pictures on our system we can host the images and we can also provide an html templating feature as well. Marketworks (formerly Auctionworks) [login to view URL] has an inventory-based API tool for eBay selling. That system is far more complicated than we need, but it is a good example.