Change Post Content with Php

Hey,

Using file_get_contents and preg_match I have figured out how to get a part of an external website and display it on my site. My question is am I able to make the post content of each blog post be the part of the external website I get?

So for example, if I needed a tv show description, I would have the url for file_get_contents to change based on the category of the post (the tv show) and custom fields (season and episode). This would then get the episode description of an external website and output it. I need to get this output and have it be the content for my post. (I could simply do this in the post template of php but if the external sites content were to change, so would my post content. I need a way to store it in my database)