Hi Naveen,
As the source system places the file one after the other, I guess when you use the Post Processing event should take care of picking the first file and process it, and it will pick another file the moment it is available.
Please confirm what kind of event you are using. Also, you should be able to check other properties for each of these event configurations which can take care of sequencing.
Regards,
Firoz N
#Managed-File-Transfer#B2B-Integration#webMethods