3E0905001 自动编号每次自动加一 如何做

自动编号每次自动加一，哪错了
<%
session("userType") = "3E-" '用户属性 A 或 B
function getDateStr() '返回 年,月 格式：yymm
dim yy,mm
yy = right(year(date()),2)
mm = month(date())
if len(mm) = 1 then mm = "0" & mm
getDateStr = yy & mm
end function

dim rs2,sql2,maxID
sql2 = "select top 1 SK_Company_No from SK_Company where SK_Company_No like '" &session("userType")&getDateStr() & "%' order by SK_Company_No desc"
set rs2 = conn.execute(sql2)
if not rs2.eof then
newID = right(rs2("SK_Company_No"),3)+1
if len(newID) = 1 then
newID = "00" & newID
elseif len(newID) = 2 then
newID = "0" & newID
end if
newID = session("userType")&getDateStr()&newID
else
newID = session("userType")&getDateStr()&"001"