How to manage a part offset and a local offset

The project is to machine parts with individual local subroutines. I tried setting the part offset:
 g01 x -[#<_offset>] y -[#<_offset>]
 g10 l20 p1 x0 y0    

and then set a local subroutine relative
  g01 x - [#<_int_width> / 2] y -[#<_int_width> - #<_mill_step>]
  g10 l20 p1 x0 y0              ; set the relative axis to

The second g10 overwrites the first g10 and the part offset is lost. In this example: \
1. what command should be used to set the origin for the part?
2. what command should be used to set the local subroutine part origin?
3. How can the first, part origin, be cleared?
4. How can the second, subroutine origin, be cleared?
Thanks, Dan

Thank you. That woried perfectly. Dan

It would be convinient to call a subroutine within a subroutine and set a local coordinates for that nested call. Assuming the above with g54 working for the first subroutine is there a command that can augment the g54 position for additional subroutine calls?