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

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