Amazon SellerCentral / Marketplace MWS API Quick Job

We currently sell products via Amazon Marketplace in the UK with a Pro account, and use the MWS API to manage listings. We need a script, which we will run via Cron once a day, that emails buyers 7 days after the last package from their order was dispatched. It will make a note of previous emails sent in a text file, to avoid repeated contact. The content of the email will be HTML and needs to be easily customisable by us. The only exception to emails is where the last package of an order was dispatched over three days after original purchase, in which case no email should be sent to that buyer. We may sometimes add order numbers to the end of the text file to block emails for a particular order, this should not interfere with the software. If you have experience making API calls with Amazon this is a pretty simple task. You must speak English. Sensible bids please.