Oracle Apex Do not close dialog after button is pressed

I have a pop-up with 2 buttons.

Update
Update to null
Deactivate

Earlier, Update was used to update the text item in the dialog to grid. So when Update is clicked dialog closes.
Update to null is used to set the value of item to null. When this button is clicked it updates to null and closes dialog.

Deactivate button was to deactivate a checkbox in the dialog. When the button was clicked it'd close the dialog too.

Now , the requirement is, the dialog should close only when Update and Update to null buttons are pressed. When Deactivate button is pressed, it shouldn't close.

Currently, Deactivate button properties are:

Action: Submit Page
Execute Validations: yes

And in processing, set value :P1_Checkbox to 'N'.
There's also a Close dialog process at the end.

The dialog is closed because by the "Close Dialog" page process. You could put a server side condition of type "REQUEST is contained in value" with value "UPDATE,UPDATE_TO_NULL". That way the close dialog process will only be fired when either of those buttons are clicked.

The "REQUEST" value on submit of the page is the Name of the button. In my example above I'm assuming the button with label "Update" has name "UPDATE" and the button with label "Update to NULL" has name "UPDATE_TO_NULL"