More flexible \multicolumn command?

[Rolf Turner]

I would like to be able to change, mid-table, the column specification
from e.g. llcl to e.g. cccc.

I can of course do this using \multicolumn, e.g.
\begin{tabular}{llcl}
a & aa & aaa & aaaa \\
a & aa & aaa & aaaa \\
\multicolumn{1}{c}{xxx} &
\multicolumn{1}{c}{xxx} &
\multicolumn{1}{c}{xxx} &
\multicolumn{1}{c}{xxx} \\
a & aa & aaa & aaaa
\end{tabular}
However this seems a bit kludgy and inelegant.  I would like to be able
to do something like:

\moreflexmc{4}{cccc}{xxx & xxx & xxx & xxx} \\

Are there any possibilities?

Thanks.

cheers,

Rolf Turner

-- 
Honorary Research Fellow
Department of Statistics
University of Auckland
Phone: +64-9-373-7599 ext. 88276