Go to SETTINGS->PROPERTIES->ROOMS->DEPENDENCIES and use the following settings:
*Requires Availability in = DoubleTop-up
*Combination Logic = Any room must be available
*Assign Bookings to = Top-Up
'''Top-up'''
*Go to SETTINGS->PROPERTIES->ROOMS->SETUP and set *Sell Priority = Hide (to not show the room type on your own booking page)*Go to SETTINGS->PROPERTIES->ROOMS->DEPENDENCIES and set *Use Prices from = Family and Double (Double needs prices for availability calculation)