How to copy value of one item to another item dynamically by click of checkbox in APEX

I have created 4 items - P17_BILL_NAME, P17_BILL_ADDRESS, When checkbox is clicked the values entered in bill_name and bill_address should be copied to p17_SHIP_NAME, P17_SHIP_ADDRESS dynamically. When checkbox is unchecked , the values in Ship_name , ship_address text field should be come NULL so that new values can be entered.

checkbox - P17_CHECKBOX

Dynamic Action - P17_COPY what should be the properties set in all those fields and SHOW & HIDE Action.