Disregard previous - forgot you can't have the same SSID in the same network. Move that AP to a separate new Network which clones the settings of the existing one. Then schedule your SSID availability on that network which will limit the scope to tha...

What's your line of sight situation and how high would the antennas be mounted? Also are you looking to serve clients off the radios while backhauling or is this just to provide a point to point backhaul?