How can I annotate the background with different colors across different Y-axes?

[#1]

The following JSL can annotate the region of 100 to 120 on the X-axis with a different color, but it cannot span across different Y-axes. How can I modify it to annotate different variable on Y-axes with different background colors for different variables?

Names Default To Here(1);

dt = Open("$SAMPLE_DATA/Big Class.jmp");

gb = dt << Graph Builder(
	Variables(X(:weight), Y(:height),Y(:age)),
	Elements(Points(X, Y, Legend(3))),
	SendToReport(

		Dispatch(
			{},
			"weight",
			ScaleBox,
			{Add Ref Line(100, "Solid", "blue", "", 5),
			Add Ref Line(120, "Solid", "blue", "", 5)}
		)
	)
);

rep = gb << report;
framebox = rep[frame box(1)];
framebox << Add Graphics Script(
	Transparency(0.5);
	Fill Color("Gray");
	Rect(100, Y Origin() + Y Range(), 120, Y Origin() , 1)
);

[#2 · Accepted solution]

You have multiple FrameBoxes when you have multiple axis (or groups or wraps or pages), so you can for example add separate graphic script to each of them. Simplified version below

Names Default To Here(1);

dt = Open("$SAMPLE_DATA/Big Class.jmp");

gb = dt << Graph Builder(
	Variables(X(:weight), Y(:height), Y(:age)),
	Elements(Points(X, Y, Legend(3)))
);

rep = gb << report;
fbs = rep << XPath("//FrameBox");

fbs[1] << Add Graphics Script(
	Transparency(0.5);
	Fill Color("Gray");
	Rect(100, Y Origin() + Y Range(), 120, Y Origin(), 1);
);

fbs[2] << Add Graphics Script(
	Transparency(0.5);
	Fill Color("Green");
	Rect(100, Y Origin() + Y Range(), 120, Y Origin(), 1);
);