Strip/Append Custom BBCode to Certain Links

[Phrost]

I'm at a complete loss here.

I'm using the YouTube custom BBCode to allow people to embed videos from YT in forum pages. But many of them are too dense/lazy/etc to add [yt] and strip out all but the video ID#.

So what would it take to do a simple replacement for anything linking to turn:

to

[yt]_KqUHQzyHFs[/yt]

As I understand it, the functionality to accomplish this is built-in to VB. Is this correct?