Getting a border box to appear on a button press.

[#1]

I am trying to open up a border box to the right of my list box on a button press, how can this be achieved? I have attached my attempted code below.

New Window("test",

		title = Text Box("test", set font style("Bold")),
			
		V List Box(
			lb = List Box( "Test", width(150),nlines( 18 ) ),
		),
		
		H List Box(
			Button = Button Box("Test",
				Spacer Box(Size(50, 25)),
				Border Box(
				Left(50), Right(50), Top(0), Bottom(50), Sides(50), Text Box("Test"),
			),
		),	
	),
);

[#2]

Here is one way this can be achieved.  As a side note -- it can be easier to understand the tree structure if you put commas at the level of the enclosing fence.

New Window( "test", 
	window:title = Text Box( "test", set font style( "Bold" ) )
, 
	window:hlb = H List Box(
		V List Box(
			window:lb = List Box( {"Test"}, Width( 150 ), N Lines( 18 ) )
		)
	)
, 	
	H List Box(
		window:Button = Button Box( "Test",
			window:hlb << Append(
				Border Box( Sides( 15 ), Left( 50 ), Right( 50 ), Top( 0 ), Bottom( 50 ),
					Text Box( "Test" )
				)
			)
		)
	)
);