Sorry, I don't understand what you mean. You take cables from the amplifier to the switch box, then cables from the switch box to each loudspeaker. That way, you can have the inside pair only, the outside pair only, or both on. If you have both on, you have to make sure that the amplifier can drive the impedance of the two pairs in parallel. As to volume control, you can get a separate volume control for the outside pair only.
If you let us know what the amplifier is and what the 'speakers are, we should be able to advise whether the amplifier can drive both pairs together, or only one pair at a time.
S.