Content API for google shopping: Need app to send product updates

We maintain our google product feed in an Excel workbook and update Google Shopping/Products by uploading a tab-delimited version as needed. We like to do it this way, as it gives us more control to do simple edits to the feed, to correct errors and control exactly what is stated in the feed (rather than integrating a feed from our website). Of course, our feed could be maintained in a simple database if it is easier for this project. PROJECT: Create an integration such that our product feed Excel workbook (or simple database) will update via the API (Content API for Google Shopping): We want to be able to update only certain products with each upload-update: ONLY those products that: 1. have a change since the last upload 2. Are new (not yet uploaded) OR 3. About to expire because they were uploaded more than 28 days ago You have two options for the project: 1. Create an interface for us to upload the changed products into (upload tab-deimited or csv or excel file) OR 2. create a small database to manage the feed information, then of course that would also be part of the project. We would prefer option #1 but if you think that option 2 has more benefits, then please describe why. It will be best to mention if you plan to create a small database or simply provide an interface for us to upload the changed products into. Thank you for your review and consideration of this project !