Creating a smaller boundary within a map

I’m currently trying to portion off a section of air_grand_canyon for a custom map.

Basically I’m making the map to be used for aerial games of “Bulldog”, but in order to do that, I need a way to define smaller boundaries for the map within the larger Grand Canyon map itself.

How would I go about doing this?

Action m
missionBattleArea. Idk don’t remember exact name.

Do I need to create a Cube around the area and assign the mission area to the cube?

In case anyone is trying to do the same thing, this works just fine:

triggers{
  isCategory:b=yes
  is_enabled:b=yes

  "Map Border"{
    is_enabled:b=yes
    comments:t="Sets Map border"

    props{
      actionsType:t="PERFORM_ONE_BY_ONE"
      conditionsType:t="ALL"
      enableAfterComplete:b=no
    }

    events{
      initMission{}
    }

    conditions{}
    actions{
      missionBattleArea{
        air:b=yes
        ground:b=no
        mapArea:b=no
        airMapArea:b=no
        killArea:b=no
        detectionArea:b=no
        killOutOfBattleArea:b=yes
        area:t="Map Area"
      }
    }

    else_actions{}
  }