Rss Feed Update Notification Link. Can It be Done?

I want a link on my site to change color whenever an (external) RSS feed is updated.
Is this possible?

 

This might work, but its over complex.

Store current rss feed file size (php filesize command) in a database.

script is ran on a cronjob, every 30 mins or however long you want it to check for an update.

it checks the fiilesize of the website rss feed against the filesize of the value in the database, if they're different, its been updated. set an updated flag to true (in database)

then just format based upon this flag etc.

there's probably an easier way, but i don't know it!

 

Thanks for the tip - I'll give it a try