how to create file names in runtime

Hi BODS Experts,

how to create file names in runtime in BODS 

EX :

My target is FLATFILE

Suppose today i have ran the my job that time i need to create the file name like :  FILENAME_YYYY_MM_DD.txt (i.e., FILENAME_2014_12_02.txt)

I will run on next week , that time file name should be FILENAME_2014_12_09.txt

Could you please help me on this .....Thanks in Advance

Thanks,

Pavan