[Xy-pic] A question about macro's in \xymatrix...

[Ben Whale]

Hi!

I have these macro's
\newcommand{\UP}{\ar@<0.5ex>}
\newcommand{\DW}{\ar@<-0.5ex>}
\newcommand{\IN}{@{>->}}
\newcommand{\ON}{@{->>}}

and I want to write things like
\begin{displaymath}
  \xymatrix{
    a'\UP\IN[r]\DW\IN[r]& a\UP\ON[r]\DW\ON[r]&a''
  }
\end{displaymath}
just to make life easier.  Now xy-pic doesn't mind \UP ,etc.. by them
selves, but if used as above the \IN and \ON are out putted as if they
were text I wanted displayed.  What can I do about this...


Ben