Extracting a URL from body of Mail message...

how could i get Safari (or OmniWeb) to go to a URL from a specific Mail message, which can be defined by subject or sender etc.? there is a message i get a few times a day who’s body contains a URL that i must visit. the subject and sender are always the same but the URL is always different. i can’t figure out the best approach. i’m trying to set a rule which will run a script but i can’t figure out a way to get the URL from the message and tell the browser to go there. any ideas?