Mail chimp Autoresponder not working

Hi,
I have been trying to workout a way for the Autoresponder to work from the API.
The work around suggested by Mail chimp,

http://www.mailchimp.com/kb/article/i-uploaded-emails-and-set-my-autores...

says to add a merge field and use that instead of the signup field.

I thought that adding a defaulted date field using the merge fields in the signup code might allow people to use Autoresponders.
I.e. all they would have to do is add the new field to the subscriber settings.
I will let you know how I get on with this.
David