Stephen,

There used to be a tool called "DDF Sniffer" from Smithware that allowed you to create DDFs based on Btrieve tables. I did a quick search and found the following sites:

http://www.cogitate.flexqtrs.com/ddsnif.htm (description)

http://www.vbxtras.com/products/DDFSniffer.asp (online store)

I hope this helps