Check out this discussion:
http://scn.sap.com/thread/3344764
Also check William's blog:
How to Use User-Module for Conversion of IDoc Messages Between Flat and XML Formats
Check out this discussion:
http://scn.sap.com/thread/3344764
Also check William's blog:
How to Use User-Module for Conversion of IDoc Messages Between Flat and XML Formats