I have added some code to your chart(untested code), that will calculate the overall and within deltas.  The left and right delta calculations require the rules for defining the boxes.
I have also added a very simple display for the 2 values.
In both cases, I am providing you with the approach that needs to be taken to give you these next enhancements to your code.  I can not guarantee perfect code, but you should see the concept and be able to take it from there 
framex_value = "";
w = New Window( "Frame size X",// opens a window with a title and this content...
		<<Return Result,
    Border Box( top( 20 ), bottom( 20 ), Left( 20 ), Right( 20 ), // window dressing 
        V List Box( // V and H lists nest to organize the display boxes
            H Center Box( Text Box( "Frame size X" ) ), // a second title, centered
            Spacer Box( size( 1, 20 ) ), // a little vertical space
            H List Box( Text Box( "Frame size X: " ), framex = Number Edit Box( "." ) ), // data entry
            Spacer Box( size( 1, 10 ) ), // a little vertical space
            H Center Box( // center the button
                Button Box( "Create graph", // this script runs when the button is pressed...
                  framex_value = framex << get ;
                   
                    column("X coordinate")<<data type(Numeric)<<Modeling Type(Continuous)<<Format(Best,12);
					New Column ( "New Y", Numeric, Nominal, Width( 5), Formula(Round(Y coordinate)));
					dt =Current Data Table();
					dt << select where( :New Y != 50503 );
					dt << delete rows;
					New Column ( "Normalized", Numeric, Continuous, Width( 10 ), Precision ( 7 ), Formula(IntenCD/Col Max(IntenCD)) );
					New Column ( "Delta" , Numeric, Continuous, Width( 10 ), Precision ( 7 ), Formula(Col Max(IntenCD)-(Col Min(IntenCD))));
					FullMat = matrix(Col Max(IntenCD)-(Col Min(IntenCD)));
					New Column ( "Normalized Field", Numeric, Continuous, Width( 10 ), Precision ( 7 ));
					
					//New Column ( "Normalized Field", Numeric, Continuous, Width( 10 ), Precision ( 7 ));
					//dt << select where( :X coordinate > (76200 - framex_value/2) & :X coordinate < (76200 - framex_value/2) );
					//dt << delete rows:
					//FieldMat = matrix(Col Max(IntenCD)-(Col Min(IntenCD)));
                    
                    New Window( " Delta results: ", modal,
						Border Box( top( 20 ), bottom( 20 ), Left( 20 ), Right( 20 ), // window dressing
						V List Box( // V and H lists nest to organize the display boxes
						H List Box( Text Box( "Full plate delta: " ), TextBox( Char( FullMat ) ) ),
						//Spacer Box( size( 1, 10 ) ), // a little vertical space
						//H List Box( Text Box( "Full field delta: " ), TextBox( Char( FieldMat ) ) ),
						//Spacer Box( size( 1, 10 ) ), // a little vertical space
						//H List Box( Text Box( "Edge of field delta: " ), TextBox( Char( 0 ) ) ),
							))
						);
						
					// Determine X Matrix
					xMat = matrix(76200 - (framex_value/2)) |/ matrix(76200 - (framex_value/2)) |/ 
						matrix(76200 + (framex_value/2)) |/ matrix(76200 + (framex_value/2));
					// The yMat is static
					yMat = [1, 0.92, 0.92, 1];
					
					// The overall delta
					overallDelta = Col Max( :Normalized ) - Col Min( :Normalized );
					
					// The delta between the lines
					withinOrangeDelta = Col Max(
						If( :X coordinate > (76200 - (framex_value / 2)) & :X coordinate < (76200 + (framex_value / 2)),
							:Normalize,
							.
						)
					) - Col Max( :Normalized ) - Col Min( :Normalized );
					withinOrangeDelta = Col Min(
						If( :X coordinate > (76200 - (framex_value / 2)) & :X coordinate < (76200 + (framex_value / 2)),
							:Normalize,
							.
						)
					);
					
					// The leftDelta and rightDelta calculations will be similar to the above withinOrangeDelta, but
					// I don't know what the upper and lower boundry values of :Normalized are  or what the interior 
					// boundrys for the calclations are 
					gb = dt << Graph Builder(
						Size( 534, 456 ),
						Show Control Panel( 0 ),
						Variables( X( :X Coordinate ), Y( :Normalized ) ),
						Elements( Points( X, Y, Legend( 5 ) ) )
					);
					Report( gb )[FrameBox( 1 )] << Add Graphics Script(
						Pen Color( "orange" );
						Pen Size( 2 );
						Line( xmat, ymat );
						
						// Add the results to the chart
						text ( 500,.92, "Overall Delta = " || char(format(overallDelta, 7,4)));
						text ( 500,.915, "Within Delta = " || char(format(withinOrangeDelta, 7,4)));
					);
					report(gb)[AxisBox(2)] << min(.91);
                    
                    w << closeWindow; // just the dialog, not the report
                )
            )
        )
     )
  
);
					
				
			
			
				
	Jim