Correlation of messages by using time

Hi,
I’m having issues with a problem that should be quite easy to solve but not for me..

I have two clients  (A,B)sending messages to two receive ports. Message type for both are .net classes written by myself. From the data in these messages i need to create a third message and send it forward.

I don’t know in which order the clients are sending the messages, so I figured I need to use the parallel shape. The problem for me comes with the correlation, since the only logic available is to compare the “ReadTime” -value coming in the message from A to “ObservationTime” coming in the message from B.

The logic for combining these two is that I know that the “ReadTime” is three seconds less than “ObservationTime”. If this is true I can process the messages.

I hope you can help me out.