TurnEntity code

If anyone has any idea how mark got his TurnEntity to work(i'm assuming some type of Quaternion equation)? IT's exactly what i'm looking for and i can't find anything like it on the net so far.

Turnentity definately uses Quats.

Not sure if this is any use ...

http://www.blitzbasic.com/codearcs/codearcs.php?code=490

Stevie