Two part form two part mailchimp list

Just like the title says, I have a two part form, the first part captures simple names and emails and this is uploaded to mailchimp list "A". The second part goes more in depth and once completed gets uploaded to mailchimp list "B".

What I want to do is automatically delete users from mailchimp list "A" if that same user has fully completed the form and is in mailchimp list "B". Manually deleting these users in list A is annoying as hell. Wondering if anybody has a similar setup. Mailchimp has told me to take a look at there API but wondering if its been done somehow through gravity forms.

Thanks guys!

Ok...it seems like a very simple thing for mailchimp to do...but apparently its above there heads and ill have to go the API route unless anybody here has an easier way.

Thanks for the help anyway!