A safe method is to use Pro/Layout or Creo Notebook**. See http://help.ptc.com/creo_hc/creo30_pma_hc/usascii/index.html#page/pma/assembly/asm_three_sub/About_Notebooks.html
It lets you store common values in a single place that can be used at a variety of levels. It's part of Top Down Design methods.
**Not Creo Layout, which is entirely different from Pro/Layout.
