If you can get the effect you are after in a stills program such as Paint Shop Pro or Photoshop, then you can export video from Vegas as a series of frames, batch convert them and re-import into Vegas.
This is a very interesting question. Your, " . . cartoon effect to an event?" . . what exactly do you mean by this? Do you mean that the colours are "flattened" -as per early pre-CG animiation? I'm thinking of Popeye and The Flinstones and the great work from H&B? If it iS this flttenning you are after then experiment with some of the coulor FXs .. is it colour curves I'm thinking of? And maybe the Sony Levels too? Add a dash of Contrast and you might have this effect ..
Apply the Threshold effect and adjust it manually until it looks right. Usually between 25 and 50% will make the event look quite anamated. Also, if you are creating this from scratch, have the actors act in a cartoonish mannor.
A program like FlixPro from Wildform might help you out. It supposedly can convert video to vector animations and achieve a cartoon-like quality. It also can convert video to Flash animations. Sadly, I've had it on my computer for over 6 months and have never gotten around to experimenting with it. Anyway, http://www.wildform.com/