Trendlines like a thresholds in Scatter Charts

[Daniel Albarracín]

Hi people,

I want to show a chart with dots (value) againts 2 thresholds (low, high) in a scatter chart. The question is, How can i do that? Because trendlines have a equation by default and there is not chance to render it horizontaly (like a linear chart with constant value).

Please, help me with this.

Thanks.