How to control header Cancel button

Helo,

I'm making a Z-table view with bol programing. I'm showing an error message when some fields are initial in DO_VALIDATE_INPUT and I want to control the header cancel button to undo the changes and exit the window, but I'm not able to catch the event in my Z-view.

When I press the cancel button system pass by DO_VALIDATE_INPUT and I want to know if user has pressed cancel or another button.

Regards.