You can accomplish this VERY easily using Bezier masking, by taking your handwriting sample and 'revealing' the writing using masks, or you can use the mask to make the writing itself if you're very talented.( I'm not)

Jason Abbott has an excellent tutorail on the VASST site on how to do exactly this as well.

Where do I find the VASST site and the tutorial?

http://webott.com/tutorial/handwriting/

I just tried this method last night and I have to say it is easier said than done. The method outlined on the page is very rudimentary and if you want to write complex, lengthy text it is a bit trickier than what the tutorial makes it out to be.

If you want to have a look at my finished clip check out my other tread

http://www.vasst.com/login.htmgets you to the VASST site.
Easiest way (I think) is to use a Bezier mask and reveal the information from a still.

Or maybe use a Photoshop gradient brush.. write the text, import in Vegas

Somewhere on this forum there's the exact description. I did it once and it worked fine..

good luck,
mark