TRADACOMS uses a header with each interchange (ORDHDR for the ORDERS message). This header message contains information that is specific to each message in the interchange.
The following is a sample TRADACOMS ORDHDR (Order Header).
STX=ANA:1+5000000000000:SOME STORES LTD+5010000000000:SUPPLIER UK LTD+070315:130233+000007+PASSW+ORDHDR+B' MHD=1+ORDHDR:9' TYP=0430+NEW-ORDERS' SDT=5010000000000:000030034' CDT=5000000000000' FIL=1630+1+070315' MTR=6' MHD=2+ORDERS:9' CLO=5000000000283:89828+EAST SOMEWHERE DEPOT' ORD=70970::070315' DIN=070321++0000' OLD=1+5010210000000++:00893592+12+60++++CRUSTY ROLLS:4 PACK' OTR=1' MTR=7' MHD=3+ORDTLR:9' OFT=1' MTR=3' END=3'