file content conversion

Gurus,

Iam doing a Idoc to file(tab delmited txt) scenario.

Idoc Structure is TPSDLS01.

for header -> Record Type Order Number Warehouse ID .......

for details ->Record Type Order Number Warehouse ID Line Number.........

My txt file should look like:

Header1.......

Detail1............................

Detail2..............................

H2...........

Detail1......................

How to do the File content conversion in this case ?