Creating The Dynamic Fields?

i want to make a form. the form will have three text fields and with two buttons. what i want with this form is when the user enters the first three fields and if he wants to add more then he will click on add more button and on the same page three more fields will appear below the first three fields. the user will then enter these three fields then if he wants to add more then he will click on add more button. so three more fields will appear below the first six fields. user will enter these fields. he will be allowed to enter upto eight or less than eight times. once he finishes with this then he will click the second button to insert this data into db.