Add horizontal line in a Dbchart for a defined value of the y-axis

Question

I have a chart DBChart with a series of values float on the axis y and datetime in the x. I wanted to add a horizontal line according to a defined axis value y. The DBChart has the function to add these lines with maximum and minimum values, but the values for line in my case will come from another dataset.

Is there a simple way to do this? What I currently do is to always add two dots to create a horizontal line.