I think that a component will need to be the answer. The ISA fields are in the header of the original message, so can’t be promoted in a schema (so far as I know) – otherwise, no problem.
Fundamentally , this is a question about how to write C# in the Message Assignment and Expression Shapes. Does anyone know of a tutorial that addresses this? My fumbling around with ‘guessing’ what is available and not in these shapes is very frustrating.
Thanks for the help.