How to post when Java Script modifies the form?

[Peter Stevens]

Hi everyone,
I am trying to sign in to a site. The form consists of a username and 
password field. No problem. But the action attribute of the Form is set 
to nil (""). So mech->submit invokes the wrong url.

Looking at the form, I find the routine below to validate the password 
and determine where the form should be POSTed to. I can figure out what 
the action URL should be. But I do tell Mechanize where it should post to?

Thanks in advance
Peter
function validatePwd(form) {
        hostName = pick some arbitrary host name ;
       if (document.login.PASSWORD.value.length < minLength) {
               ...
       } else {
               document.login.action="https://"; + hostName + 
"/some-login-script";
               document.login.submit();
       }
}