copy the contents of a SOAP header

Does anyone know of an easy way to copy the contents of a SOAP header from
an 
incoming response to an outgoing message within an expression block?
Property 
schemas et al. seem like overkill when you want everything, but I'll do
that 
also if it works. I'm dealing with a login msg - transaction msg - logout 
that must utilize the same session id (stored in the header) in each
message.

Not having luck so far?