It's not all or nothing.

Just turn off the MIDI Rx (receive) switches for the parts in the XP60 performance you *don't* want to accept/respond to MIDI data coming from your sequencer.

You can also turn off the MIDI Tx (transmit) switches (presumably) in your JX50 for those channels you do *not* want sent to the XP80.

See your XP60 manual p. 183, "Playing the XP-80 sound source from an external MIDI device."

Have I understood your question correctly?