Our own John Rofrano just wrote and posted a 30fps to 29.97fps slowdown script that is exactly what users of DV Film's Epic 1 software need in order to use Canon DSLR footage (which is exactly 30fps) in a standard HD Bluray project (which is a slightly slower 29.97 fps). This script is excellent. It only affect clips that need the slowdown and turns off smart-resampling while it is at it so there is no chance of ghosting. There are a couple of other useful scripts here as well:
http://www.johnrofrano.com/vegasscripts.htm