Auto approve pending (previously published) front end posts with only one meta change

Hey there! Shortened description: I need plugin that checks what post (meta) fields have been changed from last revision when modified, and auto approve submission if only one meta field is change (price). No modifications to existing plugins is to be done, all development should be contained in a custom plugin. All plugins will be provided. Full description: I run a site based on Easy Digital Downloads, with Front end submissions-plugin, to create a marketplace. The site is like the one used by the theme, Marketify. Here is the demo: [login to view URL] Users can create posts (custom post called "Download") in a vendor dashboard, and in the settings these posts can be set to be auto approved, or need approval from admins. I want to manually approve all "downloads" the users create, but I would like to auto-approve in one case: When an already approved (published) post is changed, and ONLY the price (meta value) is changed. Example: The author behind a download sees that his product is popular, and decides to increase the price. He enters the vendor dashboard, edits the download to have an increased price. Currently, this leads to me having to re-approve the download. I want this download to be auto approved, since any hour the (popular) product is unavailable could cause lost sales. This would require some sort of comparison between revisions of the post. Get in touch if you have any questions.