I have created a master template file with links to a source workbook
containing prices. As prices change from time to time, I save the old rates
in a separate file and update the rates in the source wookbook so they are
always current. The template file is then used as a master document and saved
as job specific file. The problem I have found is when you open more that one
job at a time the rates can change without prompting.

e.g. If I open a recent job and update once I open the file to make sure I
get the latest rates, then open a second job which may have a old set of
rates, the rates in the recent job (which should be current) revert back to
the older rates for some reason. Likewise if I open the old job first and
dont update the rates, then open a current project and update the rates,
then the rates in the old job change to the new rates without prompting.