Cocoa spell checking and HTML tags

Maybe some of the Cocoa programmers in the audience have the answer to this question.

How do I get the spell checker to ignore HTML tags? I note that Mail does it, for instance. But a generic NSTextView does not.

I’ve combed the list archives at cocoa.mamasam.com etc. etc., but I’ve found no answers yet.

The idea is that the spell checker in NetNewsWire Pro’s weblog editor should ignore HTML tags.