eBay tweaks

I would like a script developed which would work with the eBay API to do the following - Check Out/Messaging System: - Once a certain item is purchased, an extra field should be provided to the buyer to capture information on design, size, etc. for that specific item. This should be linked to eBay note. This should be a required field for checkout for certain items requiring input from the buyer. Send out multiple messages: - Script to send the same messages to multiple users, select from templates and send to multiple users e.g someone purchases a certain product. A message/e-mail should be sent based on a template offering extras for that product. Automatically update stock based on criteria: - I would like to update the quantity for certain products automatically. Lets say I choose A, B & C products to have this feature enabled. Their product quantity should automatically be updated when it reaches '1 No.' available, this would be updated back to '3No.'. Automatically create sales: I would like the script to create sales automatically for certain products using a choose interval e.g every 1/2 days. Once it ends it should automatically be created and end at a chosen time. Please send me a message to let me know how you propose to have this done. Is there a particular script/application that you could provide to meet these functions?