I executed the same thing but I am getting an error and also in the data table the column name is being displayed instead of the values.
Names Default To Here( 1 );
Error = expr(New Window("JMP ALERT" , <<Modal, alert=Textbox("Please select the required fields."), alert<< set font size(11), <<set font name("Calibri"), ButtonBox("OK")));
Openwindow = expr(Distribution << open window);
dt = Open( "C:\Users\vgarlap1\Documents\JMP Application\2016_37742-Dist.XLS_Length_n (2).jmp", invisible(1) );
Distribution = New Window( "Distribution Fit",
	<< modal(),
	<<On Close( Close( dt, nosave )),
	V List Box(
			Spacer Box(Size(2, 4)),
			Title = Text Box("AFIS Length Distribution Fit"),
			Title1 = Text Box("(Customized procedure for Ln)"),
			Title << set font size(12), << set width(240), <<set font name("Calibri") ;
			Title1 << set font size(11), << set width(240);
			Spacer Box(Size(4, 6)),
			H List Box(
				Panel Box( "Column List",
					ColListData = Col List Box(
						all,
						width( 250 ),
						maxSelected( 1 )
					)
				),
			V list box(
				Panel Box( "Column Selection",
					Lineup Box( N Col( 2 ),
						Button box("X Column", << Set Function(Function({this},(this << sib) << Set Items((ColListData << Get Selected));))),
						colListX = ColListBox(dt, Min Items(1), Max Items(1), N Lines(2)),
						Button box("Y Column",  << Set Function(Function({this},(this << sib) << Set Items((ColListData << Get Selected));))),
						colListY = ColListBox(dt, Min Items(1), Max Items(1), N Lines(2)),
						Button box("BY Column",  << Set Function(Function({this},(this << sib) << Set Items((ColListData << Get Selected));))),
						colListBy = ColListBox(dt, Min Items(1), Max Items(1), N Lines(2))
					);
				),
				H List box(
					Button box("Ok",
						//<<On Close(nosave),
						If(nitems(colListX << Get Items())<1 | nitems(colListY << Get Items())<1 ,
							Error,	
						);
						
						
						dt= currentdatatable();
						icol = dt << Get Column Names();
						Nrows = N Row (dt);
						x_selection = colListX << get items;
						y_selection = colListY << get items;
						by_selection = colListBy << get items;
						
						New Column( "Model",
							Numeric,
							"Continuous",
							Format( "Best", 12 ),
							Formula(
							Parameter(
								{p = 0.29, x0 = 15, m0 = 1.2, x1 = 30, m1 = 5},
								p * (1 - Exp( -(Eval(x_selection)/ x0) ^ m0 )) + (1 - p) * (1
								-Exp( -Eval(x_selection)/ x1) ^ m1 )
								)	
							),
						);
						nlin = dt << Nonlinear(
						SendToByGroup( Bygroup Default ),
						Y(Eval(y_selection)),
						X( :Model ),
						Iteration Limit( 1000 ),
						Unthreaded( 1 ),
						QuasiNewton BFGS,
						//Newton,
						Finish,
						By(Eval(by_selection)),
	
						);
	
					rnlin1 = Report( nlin[1] );
	
						//colListX << Clear Selection,
						//colListY << Clear Selection,
						//colListBy << Clear Selection
						
					),
					ButtonBox("Cancel", Distribution<<CloseWindow),
					ButtonBox("Remove",
                        colListX<<RemoveSelected;
                        colListY<<RemoveSelected;
                        colListBy<<RemoveSelected;
                    )
				)
			)
		)
	)
);