dynamic Target folder/directory simple file pass scenario

Hi PI Gurus,

For a simple file pass scenario no  mapping/IR objects

How can we determine the Target  directory   based on the source file name ( not  payload )

i.e  if the source file name is  "XXXX_100"  I need to move this file to directory  ABC\"100"\XXXX_1000 .

similarly  XXXX_200  to  directory ABC\"200"\XXXX_2000.

I know we can use UDF  but  payload does not have the field  and the file mapping may be complicated

as its a flat file .

what I am looking for is with out any mapping and IR objects I want to dynamically determine target directory based on the source file name .

any clues how to do achieve this ?

Thanks,

Raj