freezing atoms in g03 optimizations

 I am trying to do a geometry optimization on a large system which contains some
 that are involved in a transition-state structure.  I would like to fix the
 portion of
 the molecule with the TS geometry and do an optimization on the rest of the
 What is the best method to freeze the TS atoms?  I have been looking at the
 ModRedundant function, but am unaware of how to create the secondary input after
 zmatrix for this.  Any help would be greatly appreciated.
 Thanks in advance,
 Joe Harriman
 Joe Harriman
 Computational Chemistry
 University of New Brunswick
 Room 228
 Toole Hall