Daisy chain multiple PCB with an existing IDC cable
What you are looking for is probably position dependant addressing, i.e. the position of the board is it's address. However it can't be done with a straight flat cable, you need to either interrupt the chain at each board or do some mechanical shifting on the ribbon like in the old floppy drive flats.
If the boards have some kind of intelligence you could devise a dynamic address assignation but you'll need some way to identify the boards (like a jumper or something to put the board in setup mode).