first you must have a table that will hold the ip of the current user of your db.
the idea is to check first this table for a particular ip, if it exist, then obviously survey has already been done on that pc. if not complete the survey questionaire first, and before closing the form save the ip of that pc to the table.
if your ip in your workplace is static then theres no problem, but if dynamic, youll also need to save the mac address of the pc.
very simple!