filtering IDOCs

Hi Experts,

I am doing one scenario... collection of IDOCs (same message type BLAORD03.BLAORD )at XI and passing via file. This is working fine. I am able to collect BLAORD03 idocs and post to File server in text file.

Now i need to collect those idocs which has a sgment E1EDP01 only and pass to file server in a text file. Here i need to fileter idocs before collecting in BPM. How this is possible.

Thnks,

Subbu