[Zope] accessing files using forms

[alice]

I want to create a site which requires Monkeys to login.

Login is done via a form.
When a Monkey first creates an account she enters her "monkey_name" and 
"password" and clicks "submit"
Now a script is called which creates a file with Id "monkey_name" containing 
"password".
This bit works fine, no problem.

The problem is when the Monkey comes back to log into to their account.
They must type in their monkey_name and password.
Now, to check if the password is right, I have to open the file named 
"monkey_name" and check if its content is the same as the password which the 
monkey typed.

This is the script I wrote: 
('monkey_name' and 'password' are variables which come from a form)

     existing_monkeys=container.objectIds('File')
     no_monkeys=len(existing_monkeys)

     i=0
     for i in range(no_monkeys):
         if (monkey_name == existing_monkeys[i]):
             if (container.monkey_name == password):
                    return "Your password is correct."
             else:
                    return "Your password is incorrect."
         else:
             return "there is no monkey by that name."

The problem is: 'container.monkey_name'

If the script is run with monkey_name = Heidi.
What we want is the file: container.Heidi
But what Zope looks for is: container.monkey_name, which of course doesn't 
exist.

I checked this by creating a file named Heidi and then a script named 
cat_file, which contains a single line:

     return container.Heidi

This returned the contents of the file Heidi without any complaints.
I then changed cat_file so that it took a parameter file_name

     return container.file_name

If I then call this file cat_file(Heidi) it doesn't work :-(

What should I do?