Customizing Welcomemail based on subforum

[Big Quiver]

I admin a forum whos subject is autos. I have a few subforums, for example, trucks, domestic cars, import cars. I'd like to customize the 'welcomemail' based on which subforum the users are registering for.

I have discovered how to edit the welcomemail through Search in Phrase but I am not too sure how to create multiple welcomemails or how to create that conditional.

Any ideas?