Freestanding facility: measured from the external wall of the facility structure closest in proximity to the school, child day-care center, or house of worship to the closest point of the property line of the school, child day-care center, or house of worship. If the school, child day-care center, or house of worship is part of a larger structure, such as an office building or strip mall, the distance shall be measured to the entrance or exit of the school, child day-care center, or house of worship closest in proximity to the facility.