My profound thanks to both Rick Quattro and Don Pratt for elegant solutions and supporting files, and to Bodvar for pointing me in the same direction. The bottom line is a fiendishly clever solution by Brad Anderson.
I never cease to be impressed with both FrameMaker and the quality of support that this group provides. I now have a separate mail folder for key exported threads, entitled 'Framers wisdom' ;-) Thanks, people. -- Steve