Very Basic Form Text Field Update Event

when the user types a FIRST NAME into the first name textbox this should update the paxname with the value and a space.when the user types a LAST NAME into the last name textbox this should update the paxname with the value therefore at the end of the process the paxname will have the full name of the person in order with spaces in between. also i would like the first name and last name values to be changed to proper case ie John Smith once placed into paxname the update process does not have to be instantaneous, it can perhaps update the paxname textbox when the focus is gone from the field in question, dont mind how it works as long as it updates.