Vim syntax files for .lhs files using \begin{code} and \end{code}

Hi, The Vim syntax file for literate Haskell programs handles code lines that begin with a '>' character fine. But in GHC much of the code is defined between "\begin{code}" and "\end{code}" pairs, and that shows up as one giant comment. Does anybody know where I might be able to obtain a Vim syntax file that handles these constructs? I made a feeble attempt myself, but Vim's syntax highlighting language defeated me. Thanks. -- Nick Nethercote njn25@cam.ac.uk