Add username/password to newly created MDB

I am trying to create a new mdb in C# using ADOX, i am able to create
DB , i want to add a username/password on that db , i have tried so
many things , cant make it to work , please help

ADOX.CatalogClass cat = new ADOX.CatalogClass();

cat.Create("Provider=" + provider + ";" +
"Data Source=" + databaseName + ";" +
"Jet OLEDB:Engine Type=5");

ADODB.ConnectionClass conn = new ConnectionClass();
conn.ConnectionString = string.Format("Provider={0};Data
Source={1};", provider,databaseName);
conn.Open("","","",0);


ADOX.UserClass user = new UserClass();
user.Name = userName;
user.ChangePassword("",password);
// FAILS HERE , cant make this method to work.
cat.Users.Append(user,password);