Checkbox And Text Box Fields - Form Automatically Generates The Appropriate #

I've done a search for this because I'm certain I'm not the first to have this problem, but I could not find the solutions. I am marginally experienced with PHP but have no knowledge of javascript. This is for a scheduling program. Prior to generating the form, the question is asked as to how many days are needed, and the form automatically generates the appropriate # of fields. They are, for this example, as follows:

Day 1, Title 1, Description 1
Day 2, Title 2, Description 2
Day 3, Title 3, Description 3
Day 4, Title 4, Description 4

I would like to add a checkbox (entitled "Same as Previous Day") that allows the user to duplicate the previous entry, populate the fields so the database is properly filled, and make the fields it just populated uneditable. So for the example, if day 2 and 3 were the same as day 1, I could select a box for each day 2 and day 3 and their titles and descriptions would be filled with the information from Day 1.