Bypass the 2-way Upstairs/Downstairs switches entirely by using a relay, triggered from AXBB_E. That just means that AXBB can override the manual switches to power-up the compressor - and have the switches turned off in this mode. You could use another output from the AXBB and a M9999 macro to automatically isolate the manual switches when UCCNC starts up, if that tickles your fancy. All do-able, just need to understand the exact control logic that you're looking to implement.