if orchA sends a message and orchB receives it then you dont need to correlate anything. if orchB is set to accept the message of that type it will accept any message and do whatever is necessary. I dont see where correlation comes into the picture. In orchB you need to have an activate receive shape which will receive the message.
At first i thought you were calling/starting OrchB from OrchA and passing a message but it doesnt seem to be the case.
Gino