Graph a step change in trend (or multiple step changes)

[#1]

Is there a way to graph a general trend that is a result of a step change (or multiple step changes)?   The general trend would be the overall line of fit.  The step changes would be lines of fit for various time periods.   Visual below.   Resaid is there a way to graph the step changes along with the general trend?

This is dummy data.  There is an obvious step change in the average (or line of fit) that explains the general trend (I guess I graphed moving average instead of trend line, but you get the idea).   How to put in the red lines?

[#2]

Right-click on the plot and select Customize. Click the Add button. You can use the Pen Color() and H Line() functions in a custom graphics script:

Pen Color( "Red" );
H Line( 0, 45, 250 );
H Line( 50, 115, 2000 );

(You can copy it here first and then paste it when you get to the Customize dialog.)

[#3]

Just thinking, let's say I wanted to show multiple step changes.  Maybe they represent events or enhancements or some fundamental change in the process or business. 

Could I do what you suggested and add variables to adjust the height (Y) and period (range of X)?  And potentially link them to averages or medians or whatever stat for that range of X?