Crossfader AB/CD switch?

[SuperKokot]

Hello,
I really like the VCI100SE mapping but the inherent VCI bugs really bother me.
I'm trying to merge my own layout and this together, and since I mix externally, I thought it would be great to map the VCI crossfader to switch between deck A/B control to C/D.
How would you go about this?

[BentoSan]

You would use very similar mappings as what Ean has on the top right of the VCI that switches between the decks. The knobs are sending out the same data as a crossfader does so it would only be a matter of double mapping these controls to your crossfader so that it switches on deck C and deck D at the same time