[Mediawiki-l] how to block http links on a specific page

[2007 at gmaskfx.com]

I want to prevent users from just posting links to external sites instead of creating new pages. Once they create new pages they can add external links but my pleas for people to add more information has been ignored. So I want to install a regexp that like the spam blocker will not let them submit links but will show them a custom page explaining the problem and telling them what they need to do. Is this a major deal?

Thanks

Adrian