ASP Authentification

i want to create a login-system in ASP... for not developing something really new - i just thought - maybe i can use the existing AD-infrastructure...
are there any code-snippets available?

so whats needed?
- "default.asp(x)"
-- checks cookie (?) - if user/pw stored in cookie = OK => open "content.asp(x)" - this page will have some select-case things implemented... i.e. is the logged in user (from cookie) a member of groupA => then include "pageA.asp(x)" etc. => is the logged in user a member of groupB => then include "pageA.asp(x)" etc. etc.

Code:
Select Case whoRu
case groupA
'include a page "(pageA.asp(x)")
'or type sql-statement
case groupB
'include a page "(pageA.asp(x)")
'or type sql-statement
case else
'etc. etc.
end Select