Custom Slideshow Pan and Zoom - Specifying Start and End Points

Hi All-

I've been using Lightroom since it first came out and have avoided the slideshow module for the simple reason that I could not specify specific start and end points for pan and zoom of photos.  Sadly, the best Adobe product, I felt, for creating a photo slideshow with pans and zooms was early versions of Photoshop Elements, which allowed very easy set up of start and end points for zooms and pans.  Is there any way to accomplish how I want the photo to look at the start and at the finish and then let Lightroom interpolate between the two?  Seems so simple, but has never been available in Lightroom...

Thanks!

Cheers,

Greg