I have not tried it so I don’t know why would get that error.
What I have it what I would expect it to look like. Maybe it doesn’t work on the Start Shape? I would think it should though.
Jon Flanders posted this to a reply to someone on my blog:
“You already can dynamically call and orchestration. If you put the correct XLANGs into a expression shape (the same that would be generated from a Call Orchestration shape) – you can dynamically call different orchestrations”
Sorry I can not be of more help on this one.