IN ORCAD 9.1
in schematic capture if you create let say 3 heterogenous part per package of a chip. after that u want to modify that to 2 heterogenous part per package for the same chip in the same library.
DONOT CREATE DIFFERENT 2 PART PER PACKAGE AND COPY THE PREVIOUS
Simple, copy and paste the pins to the third heterogenous part, delete the second part and rename the reference designator of the third part as U?B? instead of the original U?C.