TN is not able to process the documents in sequence

Our Partner is sending three documents in 6 sec difference in sequence. But Trading Netowrks is not processing these documents all the time in sequence. Sequence is crucial to our application. TN shows Date recieved time in out of sequence for these documents. Do you guys guys know any way to force sequence in TN.
Thanks in advance,
Ramesh Reddi

In the processingRule–>Action tab specify synchronously