*Create the virtual room by making a copy of the real room at the SETTINGS -> PROPERTIES -> ROOMS menu.
*Set "Sell Priority" to "Hide Room" if you do not want to display the virtual room on your booking page.
Go to PROPERTIES -> ROOMS -> DEPENDENCIES and set set:
*in Availabilty "sell priority" = "hidden"
*in Dependency "Requires Availability" = real room
*in Assign Bookings = real room
*Set "Sell Priority" to "Hide Room" if you do not want to display the virtual room on your booking page.
'''Custom Availability'''