My need as stated earlier in the thread is similar to the need of Rich and also to the need of Ian earlier in the thread. Basically, the current software allows you to associate one or two masters with a zone, but that is the same every time the zone is used. We need to open only one master at a time, but to be able to choose which one to open depending on the program or day. I want to normally use hard water to conserve softener salt, but then rinse all of my drip zones with soft water after use, to avoid calcium deposits. Ian and Rich want to choose RO or fertilizer as sources. Neither of us need to open two master valves for a single zone at the same time, it is either/or. Ideally, you could select the master for each zone within the program. Having to do this by controlling the master valve as a simultaneous program seems overly complicated and prone to mistakes.