The only way is to pretend having no FF
card when making reservation and checking-in and reclaim miles after completing the whole journey.
You'll need to save all boarding passes and send a xerox copy of the ticket and originals of the boarding passes to respective freq. flyer customer care centers from which you want the miles to be credited. They will see you've flown more segments than you claim, but since the rule is "no boarding pass no miles" it won't matter.
I don't know how it works with your ff programs when it comes to crediting miles for different booking classes, but in general it should work.
I've done it for my dad splitting miles between CSA OK Plus and Swiss Travel Club when he flew OK and CX PRG-FRA-HKG-AMS-PRG (PRG-FRA, AMS-PRG with OK, the rest with CX).
[Edited 2004-09-19 04:06:44]