active directory lookup

[Jerry]

I have a requirment where I need to check if a given user has been defined
in the active directory list of users..
I've looked at directoryentry, directorysearch but I'm getting no where..

1. Does the code that needs to seach the active directory have to have
admin rights?
2. When I define the filter for my search in the directory entry, I get an
error "dn syntax error"..

dim ade as directoryentry(LDAP://Users,dc=mydomain)
dim search as directorysearch(ade)
dim result searchresult

'userfname.userlname are passed as args.
search.filter = "(cn=" + userfname.userlname + ")"
result = search.findone

the last line causes the error....

thanks
Jerry