The work-around for importing pieces of data into a bound form involves importing the xml and then parsing it to fill only those fields you're looking for at that point.
You can find more info on that process in the following posts
Mark Schenecker, "Import an xml file into adobe designer field using javascript" #3, 5 Jul 2005 1:02...David O'Hanlon, "Retrieve data from XML file" #3, 2 Jul 2005 5:51 am
Also note that you can always export as xdp to get ALL the field data -but if you export as xml it only exports the data tied to the schema.
On (re-)import, the xdp will attempt to fill all of the field in the form. The xml will attempt to fill all fields bound to the schema -even if the imported schema has no entries in the fields, it considers them tto be empty fields and will replace any data existing in the form with the blank from the schema.
And one more point - it is possible to bind fields to more than one data source. This doesn't mean that you can bind fields to more than one schema -rather that you can bind a field to both a governing schema and webservice. Unfortunately I'm not terribly skilled at this yet so I hesitate to give instructions. It's in the documentation, though.
Good luck!