function Validate()
{
    var themessage = "You are required to complete the following fields: ";
    var allgood = true;

    if (document.booking_form.name.value=="") {
      themessage = themessage + " - name";
      allgood=false;
    }
     if (document.booking_form.number.value=="") {
      themessage = themessage + " - tel";
      allgood=false;
    }
     if (document.booking_form.email.value=="") {
      themessage = themessage + " - email address";
      allgood=false;
    }
     if (document.booking_form.booking_date.value=="") {
      themessage = themessage + " - booking date";
      allgood=false;
    }
    if (document.booking_form.booking_time.value=="") {
      themessage = themessage + " - booking time";
      allgood=false;
    }
    if (document.booking_form.details.value=="") {
      themessage = themessage + " - details";
      allgood=false;
    }
    // and so on and so forth for each field

    //alert if fields are empty and cancel form submit
    if (!allgood)
         alert(themessage);


    return allgood;

}