chainload bootmgr on same partition

[Greg]

I've recently migrated from using syslinux to grub2 on a bootable USB. One
of the options that I need is to boot WinPE. All bootmanagers, kernels, etc
reside in one partition. In syslinux I had a working menu entry like this:
  COM32 /boot/syslinux/chain.c32
  APPEND fs ntldr=/boot/WinPE_Vista/bootmgr

#1: Is there a similar method available in grub2? I've tried various
syntaxes of chainloader /boot/WinPE_Vista/bootmgr without much luck.

#2: If the answer to #1 is no, then my current solution is to chainload
syslinux using a syslinux MBR image. This is a total hack. I searched for a
way to boot ldlinux.sys but couldn't find anything. Is there a solution to
load/chainload syslinux that I've missed.

Thanks,
Greg