How would you counter when your arms are locked and an opponent is chopping at your head?

Past masters made things easy for us. They classified all attacks into four categories, namely striking, kicking, felling and chin-na. This video series introduces chin-na techniques. What would you do if an opponent grips your arm, uses it to lock your other arm, and simultaneously chop at your head? Indeed, if you apply this chin-na technique in your sparring or fighting, many people would not know how to respond.