Create custom php page or another database from wordpress

Hello,
This is the first time I am developing a wordpress plugin. Actually, that is a url rewriting plugin which generates alternate expiring urls according to some pattern in the posts or page.

The idea of plugin is like this
1. It will search for a particular URL pattern in the posts and page content.
2. Then generate a new custom URL using a particular algorithm taking the original URL as parameter. The new URL would be of the same domain as that of the wordpress blog.
3. It will then store the new URL and the old URL combination in the database with timestamp.
4. Then when that new URL will be accessed, the page will search the database for the original URL and the timestamp. If the time difference between the generation of the URL and current time is appropriate, then it will redirect to the page accessed by the original URL, otherwise will give error.

I have done the part of replacing the URLs in posts and page with the new generated URLs. But now the problem I am facing is to redirect the page accessed from newly generated URLs to the original URL.

Is there any way to generate a page with custom php code in wordpress and access it using some particular link, or some kind of method to load a particular page when a particular type of URL is called.
Another way I can think is either to access wordpress database from an outside page, or create some another database from wordpress.

Please guide me with any workaround for this case.
Thank you.

With Regards:
Rahul Bairathi