Here's one tutorial [webreference.com] on the subject from WebReference.
<added> However, you might be able to get the result you describe by nesting framesets. If your target frame is actually a "level-2" frameset, then you could target that frame (which actually contains 2 frames) and replace it with a similarly defined 2-frame frameset.
It gets complex -- I've done this one time about two years ago and I was talking to myself for long while afterwards.
I've sent you a representative URL -- look to your "Sticky Mail" </added>