[XeTeX] Fontspec question

[David Denton]

Hello XeTeX users,

This is very much a newbe question, the answer to which is probably
quite obvious, but I have not been able to solve it in looking at the
documentation. I am using Xelatex under Miktex 2.7. My project
involves a main font in with words and phrases scattered throughout in
an alternate font. My main font is established as follows:

\setmainfont[Mapping=tex-text]{LMRoman12}

I define my alternate font as follows:

\newfontfamily\cr{BJECree}

To invoke the alternate font I do: \cr

But how can I easily switch back and forth between the main font and the
alternate font without having to redefine the main font each time.

If I define the main font thusly:

\newfontfamily\lmr{LMRoman12}

and switch back and forth between \lmr and \cr I do not seem to be
able to keep the latex mapping. Any ideas would be appreciated.

-- 
Best regards,
David