How to use "unless" for Array in Ruby?

        if lineItemQuantities
          lineItemQuantities.each do |lineItemQuantity|
            if lineItemQuantity["lineItemQuantityType"] == "Accepted"
              outstanding_value  = outstanding_value + lineItemQuantity["quantity"]*(lineItemQuantity["unitPrice"] + lineItemQuantity["unitTax"])
            end
          end
        end

How to use unless in my above code? I tried using it by referring how to not iterate nil array ruby? But was not able to do that.