Creating a new table by selecting columns from an existing one using cell selection callback

hello, i want to create an application which reads the given table and allows user to select columns and then recreating a table with the selected columns. I am working on forecasting electricity prices and getting data from https://www.epias.com.tr/en/. my code is working on a fixed table template and that is date-hour-price. But some excel files have more than one currency and the table can be date-hour-turkish lira-usd-cad. i want user to be able to choose currency and work on it. reads table and user selects columns (date-hour-try/usd/cad) and creates new table consisted selected columns.Reading table and formatting is done but. selection callback and confirm push button callbacks are not working properly. it creates a table but table is irrelevant. it's like i can't keep the read data and create an empty one.

• % app.CallingApp = mainapp;

[filename, ~] = uigetfile({'*.*';'*.xlsx'},'Search Data to be Read');

T=readtable(filename,"Sheet",1);

app.UITable.Data=T;

T.Properties.VariableNames{1} = 'Tarih';

T.Properties.VariableNames{2} = 'Saat';

T.Properties.VariableNames{3} = 'Tuketim';

app.UITable.ColumnName=T.Properties.VariableNames;

T.Saat=datetime(T.Saat,'Format','HH:mm');

T.Tarih=datetime(T.Tarih,'Format','dd.MM.yyyy');

T.Tarih.Format='dd.MM.uuuu HH:mm';

T.Saat.Format='dd.MM.uuuu HH:mm';

T.Tarih= T.Tarih + timeofday(T.Saat);

x=T.Tarih;

y=T.Tuketim;

app.T=table(x,y);

% Cell selection callback: UITable

function UITableCellSelection(app, event)

app.SelectedColumns = event.Indices;

function ConfirmButtonPushed(app, event)

app.SelectedColumns =app.T app.UITable.Data=app.T;