Well - here's something that you can do if you guys are itching to do a rack focus effect on a completely infocus shot (this can potentially take a while.

Copy your video track three times (or as many times as necessary to have a BG, forground, and however many objects that you want to move the focus to.)
Mask your forground object on your top track
mask each track after that to the object that you want to shift the focus to,
then put down the BG layer.

Put down a couple of linear blur filters on each layer
then make sure that on blur is going vertically bluring, while the other is doing horizontal blurring (to give it an omnidirectional blur) - or use a gaussian blur filter (not sure if one way renders faster than the other)
then simply adjust each layer to the amount of blur you want ont it (making sure that the BG is out of focus (or foreground - depending on the direction of your focus movement)

Then render for hours (after spending a lot of time masking each object)

It's not gonna be fast (but it's gonna get you what you want if you really need it and didn't do it in the first place)

I'm not sure if you may need to feather the masks somewhat to maintain the illusion of reality for out of focus objects (as they would actually "increase" in "size" as they go out of focus)

I've never done it - so I may be mistaken - but logically it makes sense (maybe there's a tutorial on the VASST site (if not I could make one if they accept them from anyone - I think they do as long as they are legit).

If you need more details - I'll be happy to oblige (other wise, I'm sure others here, will help you too)

Dave