Controller Extension to Show a dialog page

Hello Everyone,

I am trying to extend a Controller "ByrMngSitesCO" , the requirement is to show an Warning Dialog page when someone click on "Apply" button .

The Dialog page needs to have "OK" and "CANCEL" button and expectation is that if the user clicks "OK" button on the dialog page, then the changes should be commited and the page should behave the same way when someone clicks on the "APPLY" button on the standard page.

I am able to show the dialog page but when I click on the "OK" button in the dialog page , it's not commiting the changes to database.