Moving field data to a history diary?

How would I go about creating an appointment date history? Example - a client
comes in on 01/01/08 and the current date field value is updated via javaScript

function freshDate() {
    var theDate = this.getField("date.today");
    theDate.value = util.printd("mm/dd/yy", new Date());
}

Next when the form is closed that date needs to be put at the top of a history
field. When the client come in on 01/02/08 the first appointment date is in
history 01/01/08 and when the form is closed again the new date 01/02/08 gets
moved to history bumps the old date 01/01/08 to another line and inserts the new
date 01/02/08 to the top. So after awhile the history field have a list of
appointment dates listed in decending order.

All help is great!