** Emacs now supports "selective undo" which undoes only within a<BR>
specified region.  To do this, set point and mark around the desired
region and type C-u C-x u (or C-u C-_).  You can then continue undoing
further, within the same region, by repeating the ordinary undo
command C-x u or C-_.  This will keep undoing changes that were made
within the region you originally specified, until either all of them
are undone, or it encounters a change which crosses the edge of that
region.
<P>
In Transient Mark mode, undoing when a region is active requests
selective undo.
<P>