XML integration for our shopify webstore from different wholesalers with different currencies and should be edited and work online

looking for a simple solution to integrate the xml files (which basically stored at cloud of our wholesalers account) to our ecommerce website. Our website made using shopify. Mapping of each xml files are different than each other. each xml file should be transferred into csv files and uploaded to shopify. this script should check the given addresses everyday and see for any changes of price, stock, name etc... price currency may different than base currency of the website. we first check the currency and define the stock exchange name for the currency and script should transform each price into given currency automatically by checking the rates (can be google currency rates). each item at the xml file may be edited or added with some extra information like tags.. so script needs to show the finished file in a spreadsheet ( can be over cloud spreadsheet of google docs) and we need to edit in bulk or each item manually. than after finish script should take the final file and transform in to csv file and upload to our domain by using our shopify login credentials. how we do now is, we download the xml file and open it over excel or google spreadsheet and edit the file, transform in to csv file with the added information and change column names and add extra columns before upload than transform in to csv file and upload to our shopify store. every other day we download the file again and see for any changes via little script and upload again the file... we need this to be optimized and make the work faster. we have couple websites and this script (or whatever you call it) should work online in a different domain of ours which can only be reached by our our admins from anywhere. if you need more information please ask before you quote.