If you have the patience, you could take K_munic's approach to a pretty sophisticated level.
Remember you can open up someting like 9 or 12 video tracks in a sequence. Take the entire shot you want to apply the effect to. Leave the unfiltered shot in track #1. Copy it to track 2 and apply the effect at x%. Copy it again to track 3 and apply it at 2X. Repeat and repeat. Now, go back and set a bunch of equally spaced edit points, put in cross dissolves and you could have a very smooth looking transition from no filter to full. (It would probably look better if you render all the effects tracks before you merge and apply dissolves.)
2 questions: a) Is it really worth this much trouble? b) are your SURE there isn't a 3rd party effect out there that would do what you want?