Change overlay close.

I want to change overlay close option depend on some logic, but when the modal is open. Is there way to do that ? I have a button and when user clicks on it it opens the modal llke this:
` var regModal = new Custombox.modal({
content: {..... },
overlay:{.... }
});

$('#regBtn').click(function(e){
    e.preventDefault();
    regModal.open();
});`

The modal has a button and when is clicked the overlay option close must be true or false, depends on the logic. I tried with:
regModal.options.overlay.close = false;, but this will be set after the current modal is closed and new modal is open (for the next modal, but not current).