Need the header of the file change dynamically

I am trying to create 10 flatfiles from a table in database. The flatfile data(more than 100 columns) will be delimited with no column names. I am running using for each loop. I need filename in the header of the file. I am not able to change the file header dynamically depending on the filename. 

Please let me know is there anyway I can change the file header dynamically.

Thanks in Advance.

BALUSUSRIHARSHA