Design an Access Database

I use [login to view URL] to manage inventory across multiple marketplaces. I currently use microsoft excel to manage the listings on solidcommerce. I need an access database that will simplify this process. It needs to be compatible with solidcommerce's excel addin tool. The database needs to be able to download all the data I require from solidcommerce; compare it to the current data in case there were changes (such as if I moved an item From one warehouse to another, or a price has changed, etc). Update the records that changed. While maintaining formulas for such fields as: sale price, warehouse location, etc. It should also let me find entries that need certain data (ie entries that are missing images, or descriptions or whatever I want to search for). Data should be easily accessible via forms. And be extensible. IE I currently sell on [login to view URL], [login to view URL], volusion. If I add Ebay in the future, I need to be able to add that in with little outside effort. Database should also let me match categories across the various platforms, assign my products to those categories. I will maintain a volusion oriented category structure. If a product, for example, is in "car parts" in my store, I need to be able to map "car parts" to the ebay/amazon/etc equivalent for easy uploading. I want to allow any item to exist in up to 5 categories. I can provide the current excel structure as a template of how things should work. Any data I change needs to be exportable to excel for uploading to solidcommerce. Any unchanged entries, of course, would not be uploaded. In short, I want it to: 1) download all current data from solid commerce. 2) compare that data to current records 3) make changes to the current data (maybe allow me to accept/decline those changes) 4) allow me to make changes to data and reupload the changed data. 5) categorize items based upon a structure I provide and map that structure to other versions (I'd do a one time map for each, and it'd remember that) 6) create feeds (a la solid commerce specs) to various marketplaces 7) allow the use of custom variables a la solid commerce specs 8) create shopping engine data feeds (csv format), that could be uploaded to various shopping portals 9) add products and then upload to solidcommerce and the various marketplaces Maybe more...we can talk about it.