This is a good question. What you are talking about is called “Time Remapping”. At first, you’d think your request would be pretty straight forward, like “hey computer, just slow this clip down gradually”. But for the software, its a more complicated issue. You have to decide where frames are going to appear in your time-line, what portions are going to be slowed down or sped up, and what in or out points are going to be honored.
Currently, time-remapping is available in After Effects. Its also coming out with Premiere Pro CS3. In the meantime if you want a cheat you could try creating a new sequence, put the clip you want to slow down in it, cut it up into sections, and then apply a different speed to each section, maybe even a dissolve from one section to the next. I’ve never done it because I have After Effects, so I don’t know how well that would work. Just another reason to upgrade to CS3!
Cal