Someone

  check1 = document.getElementById("Year").value;
  check2 = document.getElementById("Month").value;
  check3 = document.getElementById("Day").value;

  if ((check1 == "Year") && (check2 == "Month") && (check3 == "Day"))
   {
    alert("Must Supply Date");
    frm.Day.focus();
    return false;
   }
  else if (!((check1 == "Year") && (check2 == "Month") && (check3 == "Day")) && ((check1 == "Year") || (check2 == "Month") || (check3 != "Day")))
   {
    alert("Date Entered Is Not Full");
    if (check3 == "Day") { frm.Day.focus(); }
    else if (check2 == "Month") { frm.Month.focus(); }
    else if (check1 == "Year") { frm.Year.focus(); }
    return false;
   }