Attached is a script that I believe simulates your data setup and two methods to create the graph you described. One uses unstacked data ( two columns) and another with stacked data.  If you are looking for rows where the Inv Prob of Y2 > Prob Y1 the unstacked (raw) data would be easier to use.
 
Note, Y1 and Y2 were simulated as uniform distributions.
Names Default to Here(1);
dt = New Table("Demo - Raw", Add rows(1000),
        New Column("Y1", Numeric, Continuous, <<Set Each Value(Random Integer(0,100)) ),
        New Column("Y2", Numeric, Continuous, <<Set Each Value(Random Integer(0,1000)) )    
     );
dist = dt << Distribution(
	Continuous Distribution( Column( :Y1 ) ),
	Continuous Distribution( Column( :Y2 ) )
);
dist << Save(Prob Scores);
dist << close window();
dt << New Column("Inv Prob Y2", numeric, continuous, <<Set Each Value(1-:Prob Y2));
//Using Unstacked data and GraphBuilder
gb = dt << Graph Builder(
	Size( 534, 454 ),
	Show Control Panel( 0 ),
	Variables(
		X( :Y1 ),
		X( :Y2, Position( 1 ) ),
		Y( :Prob Y1 ),
		Y( :Inv Prob Y2, Position( 1 ) )
	),
	Elements(
		Smoother( X( 1 ), Y( 1 ), Legend( 25 ) ),
		Smoother( X( 2 ), Y( 2 ), Legend( 27 ) )
	),
	SendToReport(
		Dispatch(
			{},
			"Y1",
			ScaleBox,
			{Min( -100 ), Max( 1100 ), Inc( 50 ), Minor Ticks( 1 ),
			Label Row( {Show Major Grid( 1 ), Show Minor Grid( 1 )} )}
		),
		Dispatch(
			{},
			"Prob Y1",
			ScaleBox,
			{Min( -0.1 ), Max( 1.1 ), Inc( 0.1 ), Minor Ticks( 1 ),
			Label Row( {Show Major Grid( 1 ), Show Minor Grid( 1 )} )}
		)
	)
);
//Sometimes it is easier to stack the data and use Bivariate instead of GraphBuilder
dtstck = dt << Stack(
	columns( :Y1, :Y2, :Prob Y1, :Inv Prob Y2 ),
	Source Label Column( "Label" ),
	Stacked Data Column( "Data" ),
	Stack By Row( 0 ),
	Number of Series( 2 ),
	Contiguous,
	Output Table Name("Demo - Stacked")
);
dtstck:Data2 << set name("Prob");
//this creates one graph with 2 curves
biv = dtstck << Bivariate(
	Y( :Prob ),
	X( :Data ),
	Group By(:Label),
	Fit Each Value( {Report(0)}),
	SendToReport(
		Dispatch(
			{},
			"1",
			ScaleBox,
			{Min( -50 ), Max( 1050 ), Inc( 50 ), Minor Ticks( 1 ),
			Label Row( {Show Major Grid( 1 ), Show Minor Grid( 1 )} )}
		),
		Dispatch(
			{},
			"2",
			ScaleBox,
			{Label Row( {Show Major Grid( 1 ), Show Minor Grid( 1 )} )}
		),
		Dispatch(
			{},
			"Bivar Plot",
			FrameBox,
			{Row Legend(
				Label,
				Color( 1 ),
				Color Theme( "JMP Default" ),
				Marker( 0 ),
				Marker Theme( "" ),
				Continuous Scale( 0 ),
				Reverse Scale( 0 ),
				Excluded Rows( 0 )
			)}
		)
	)
);
Here are the two graphs:

