[Zope] how to use a form to authenticates a user?

[Nils Wiegandt]

want that u insert your name and password in a form which a method
proofs to authenticates u.

made this so far:
1. the form

<form action="proof" method=post>
name<input type="text" name=name><p>
Password<input type="password" name=pwd><p>
<input type="submit" value="submit"><input type="reset" value="delete">
</form>

2. the method

<dtml-if
"acl_users.getUser(REQUEST.form['name']).authenticate(REQUEST.form['pwd'],REQUEST)">

password right
<dtml-else>
password false
</dtml-if>

that's it, but doesn't work, after submit zope opens the own acces
window,which also doesn't work if I enter my name and password!?

Thanks for help