Run WinPE from a directory

Hi,

I've installed WinPE to the hard drive and added it as an option in the Boot
Manager. It all works as advertised.

However, the instructions only explain how to do this with the Boot.WIM file.

What I would like is to point the Boot Manager WinPE entry to a directory
(created with 'imagex /apply boot.wim 1... etc') instead of pointing it to
Boot.wim.

That way I can make quick changes to this directory (add stuff to System32,
for example) without having to go through the whole dog-and-pony show of
having to generate Boot.WIM after every little change.

Can this be done and if so, how?

Thanks muchly in advance as always.