Filename for aditional file(s) in SFTP to SFTP scenario

I got the following scenario:

• SFTP-Server with four files, one optional
• If the files exist, the PI should transfer them all at once using the same filename
• SFTP-Sender configuration:
• Mainfile: it200n_\d{8}.txt
• additional Files(s): file1,file2,file3

There is no mapping and no service interfaces.

Dynamic attributes are used to move the filename from sender to receiver.

The problem now is, that it generates the following filenames:

it200n_20130605.txt

it200n_20130605.txt_it2012_20130605.txt

it200n_20130605.txt_teven_20130605.txt

How can I prevent the receiver to add the masterfilename to the additional filenames?

I would like to transfer all files at once because there is a script on the receiver side, that needs to do something, after they are all there.