External Data structure

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Hi,

I am writing a new program, from this program I need to pass all the fields in 
a file to called program. I thought, I can do this by defining the file as 
Externally described data structure, but 50% of the fields in this file are 
also defined in another data structure. I can't rename the fields as Called 
program updates some of the fields in the data structure. I want to avoid the 
pain of moving each & every field of file to work field and Work field to File 
field. I have 600+ fields in the file.

Any thoughts....  Thanks in advance

Chandra.