Android : ViewPager block forward on page

There's a lot of questions and solutions on how to block swipes in an ViewPager.

Example: Control which directions the ViewPager can be scrolled, dynamically with UI feedback

However I would like to only block forward swipe on an specific pages (I have a form and register button that takes next page programatically)

Example: Page 1 -> swipe <- Page 2 -> swipe <- Page 3 (form) -> button -> Page 4

Tried to extend class ViewPager with methods onInterceptTouchEvent and onInterceptTouchEvent but when doing so I can't get the button to work because everything is read as MotionEvent.ACTION_MOVE so don't know when to let the event to go thru or when to use return false;