Hiding Rows in String Grid...

Hi,
  I have been trying to duplicate the hide/unhide - collapse/expand of rows in
a string grid ala the Object Inspector with the + or - before the appropriate
fixed row title.  I have been successful up to a point.  I have any number of
rows that may be shown or hidden.  I have been using a row height of 0 or -1
to try to eliminate thick gridlines between adjacent rows... but can't seem to
eliminate missing gridlines under some circumstances... anyone have a good
method for hiding rows?
Thanks,
Mark