PM keyword messages

[cd1986]

I'm wondering whether anyone has come across anything like this (otherwise i might post a request for it) or might have an idea of how to easily do this.

Basically, a user goes into his profile and is able to add certain keywords to a field. As well as this, they can add a message that will appear if another user tries to send a PM that contains any of these keywords.

I don't want to block off PMs from users, just limit it this way, as a type of re-direction. In my case, i get PMs about services i sel on one of my websites, and i'd like to bring up a message with a link to the order page / support page, if any specific keywords relating to these purchases are used in the content of a PM.