Midi Control Switches and Hello

On my midi control surface I have one slider which needs to control two sliders in my Max patch, and what I want is a button or toggle which switches between which slider the midi controls.

If that isn't clear, or doesn't make sense maybe this will clear things up.
When a switch is on the midi controls slider A
when the switch is off the midi controls slider B

Also Hi I'm new here and THANK YOU, all, very very much in advance for helping me.